1 

# WREG/CP-002 

# IES-66

mal 5% 

### :3 Q 

### w Mfo m 

### .cy" 

# LARVALEXCLUSIONSYSTEMSFOR POWER 

# PLANT - 

# w COOLING

# WATER INTAKES ProceedingsoftheWorkshop Heldat Shelter Island Inn, San Diego, California, February7-8, I978

ARGONNE NATIONAL LABORATORY, ARGONNE, ILLINOIS Operated 

## for the 

## U. 

## S. DEPARTMENT 

# OF ENERGY under Contract 

## W-31-109-Eng-38The facilities of Argonne National Laboratoryareowned by the UnitedStates Government. Underthe terms of a contract (W-31-109-Eng-38) betweenthe U. 

## s. Department ofEnergy,Argonne Universities Association andThe University of Chicago,the University employs the staff and operatestheLaboratory inaccordance withpolicies andprogramsformulated,approved and reviewed by theAssociation.

MEMBERSOFARGONhTEUNIVERSITIES ASSOCIATIOiK The Universityof Arizona Carnegie-Mellon University Case WesternReserveUniversity TheUniversity of Chicago University of Cincinnati Illinois Institute of Technology University of Illinois Indiana University Iowa State University The University of Iowa Kansas State University The University of Kansas Loyola University Marquette University Michigan State University The University of Miihigan- University of Minnesota University of Missouri Northwestern University University of Notre Dame The OhioState University Ohio University The Pennsylvania StateUniversity PurdueUniversity Saint Louis University SouthernIllinois University The University of TexasatAustin Washington University Wayne StateUniversity The University of Wisconsin



## NOTICE
This report was prepared asanaccount of work sponsored by anagency of the United StatesGovernment. Neitherthe United States Government nor any agencythereof,nor any of their contractors, subcontractors, or any of their employees, makesanywarranty, expressedorimplied,orassumes any legal liability or responsibility for any third party!s use, orthe results of sz& "SF, =fzzy i~fcr!~=ti~~, apparatus,product or processdisclosedinthis report, or representsthat i t s u s eby such thirdpartywouldnot infringe privately-owned rights.

Available from NationalTechnical InformationService Springfield, Virginia 22161

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## ANL/ES-66 

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## ARGONNE NATIONAL 

## LABORATORY 9700 South Cass 

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# LARVAL

# EXCLUSION SYSTEMS 

# FOR POWER PLANT COOLING

# WATER 

# INTAKES

PROCEEDINGS 

## OF THE WORKSHOP 

## HELD AT SHELTER ISLAND INN,-SAN DIEGO, CALIFORNIA, 

## FEBRUARY 7-8, 1978

Rajendra K. 

## Sharma Argonne National Laboratory and John B. 

## Palmer Southern California Edison Co. Editors



## August 1978

COSPONSORS: ARGONNE NATIONAL LABORATORY ELECTRIC POWER 

## RESEARCH INSTITUTE SOUTHERN 

## CALIFORNIA EDISON COMPANY237


### to the source water body. Since considerable "handling"of organisms 

### is involved in use ofthis concept, biological effectiveness depends on efficienthandling atvarious stages in the system. The intakevelocity should be very low so 

### that if there is any impingementof larvaeon the screens, it is gentle enough not to result 

### in damage ormortality; thewash spray for the screen panels or the baskets should be low-pressureso 

### as not to result 

### inmortality; the sluiceway should provide smooth flow so 

### that there are no areas ofhigh turbulence;and enough flowshould be maintained so 

### that the sluiceway is not dry at any time. returned to the sourcewater body, theirmortality should not be significantly in excessofthe expected natural mortality for their stages. velocity can be reduced to

### the point that impingementof larvae, 

### if any, is not detrimental and the wash systemcan be designed so 

### that debrisand organismsare separated to a great extentand spray wash for the organisms 

### is not too forceful. The design of the sluiceway,however, leaves much to be desired. rates for larvae under natural conditionsand under the influenceof

### such an impingement-return cycleare needed before any definitiveand long-term commitmentsaremade to developand improve upon this concept.

up water aswell as once-through cooling for sites on freshwater, estuarine, and marine locations. is recommended that investigationsbe conducted whichwill result in

### furtherdevelopmentof this concept. Also, it appears that,due to design flexibility, the single-entry, double-exit screen has a 

### slight advantageover the conventionalvertical traveling screen. Finally,after the organisms are 

### In this whole sequenceof.operation,the intake
Also, comparative determination, evaluation,and assessmentofmortality

This system offers proven hardware technology which is feasible for the screeningofmakeConsidering the technologicat advantagesand flexibility in the use of this concept, it



### RECOMMENDATIONS As 

### a resultofdiscussionsat the workshop, the following recommendations aremade: 

### 1.

2.



### 3.
4.



### 5.



### 6.
7. 

### On basis ofpresent knowledge,no sound arguments on an ecological basis can be forwarded to screen fish larval forms at all power plants. However, if economics are favorable,or if the cost-benefit analysis dictates it, there are technological options which shouldbe investigatedfor screening fish larval formsat the cooling water intakesofpower plants. A 

### detailed comparativecost evaluationof various concepts is needed. evaluation should be in terms of the design, construction, operation,and maintenance ofvariousalternatives. A 

### cost-benefit evaluation should be attempted only on a 

### site-specific basis because the value of the species to be protected can significantly a'ltersuch an evaluation. Geologic and hydrologic factors permitting,the subsurfacecollectorconcept is themost effectivefor larval exclusion. Further investigationsarewarranted on screening efficiency, debris removal,and biofouling control ofperforated-pipe,profile-wire screen,and other such intakes. The hydrodynamic characteristicsof screening--suchas orientationof

### screening surface to flow,which could improvebiological effectivenessof this screening concept--shouldbe investigatedfurther. Biological effectivenessofporous dikes is unknown at 

### this time. Field demonstrationsareessential prior to any long-term comnitments todevelopment of

### this technology. Further researchand developmentof artificat filterbeds is

### notwarranted because of operational and maintenanceproblems. Fine-mesh traveling screensoffer long-term,proven technology. effectivenessfor thewhole cycle, from impingementto

### survival in the sourcewater body, should be investigated thoroughlyprior to implementationof this option. The cost

However,biological

$7 U.S. GOVERNMENTPRiNTlNG OFFICE: 1978-750-186/2801FOREWORD
Section 316(b) 

### of the Federal Water Pollution Control Act Amendments of 1972 (PL 92-500) states, “Any standard established 

# ... applicable to a point source shall require that the location, design, construction, and capacity of cooling-water intake structures reflect 

### the best technology available forminimizing adverse environmental impact.” the actbecause of concern about the potential ecological impact resulting from passing a large amount of water through intake screens at thermal power 

### plants. Passage of aquatic organisms through the power plant 

### is called entrainment. The designing of intakes and cooling systems

### toreduce entrainment losses 

### to fish populations and 

### the testing of their effectiveness require a combination of engineering and biological expertise. several approaches to reducing entrainment losses. entering 

### the cooling system by application of various diversion and screening devices. 

### is toreduce the mortality rate among those organisms passing through the cooling system by minimizing the stress 

### towhich they are subjected.
Intakeswas to evaluate the status of various methods forprevention of larval fish entrainment. Concepts covered include: artificial filterbeds; subsurface collectors (wells); porous dikes; fine-mesh screens;perforated pipes; single-entrance, double-exi

### t screens; and prof

### ile-wire screens. promising domain of applicability (e.g., ocean, estuary, lake, river; once-through cooling system; offstreamcooling system), and to define the status of current knowledge and investigations on the engineering and biological effectiveness of each concept. For most concepts, 

### the demonstration of engineering feasibility is farther ahead than the demonstration of biological effectiveness. Recommendationsfor future research are also identified in

### the synthesis section. 

### This sectionwas included 

### in

There are

A second One is to reduce the number of organisms



### The objective of 

### the Workshop on Larval Exclusion Systems for Power Plant CoolinglJater



### An attempt has been made inthe synthesis section of 

### this report to specify the most

Itwas c’learatthe workshop that substantial progress 

### is being made inunderstanding larval behavior and avoidance. Several years ago, itwas usually assumed that fish larvae were completely planktonic, i.e., they exerted no control over theirpositions 

### inthe water body. However, recent experiments indicate that fish larvae are capable of swimming and actively avoiding certain objects. ing intakes that would produce 

### a hydrodynamic field to promote larval avoidance. Increased understanding in

### this area should prove valuab7e 

### indevelop

### August 1978 Robert Goldstein Environmental Assessment Department Electric Power Research Institute Palo Alto, California



### iiiACKNOWLEDGEMENTS The workshop was cosponsored by Argonne National Laboratory (ANL)

### ,Electric Power Research Institute (EPRI), and Southern California Edison Company (SCE). funding, SCE hosted the workshop, and ANL prepared and printed the proceedings. ANL effort and involvement was made possible as a result ofgrants from the U. S. Nuclear Regulatory Commission We thank the authorswhose cooperation has resulted intimely publication of these proceedings, and we thank the participativeaudience whose involvement indiscussions made this a worthwhile and productive workshop. efforts inediting the manuscripts. EPRI provided most of the

Thanks are also due toShari Zussman and Dee Wyman for painstaking

iV

### CONTENTS

Foreword. R. Goldstein 

## ................................. Acknowledgements 

## .................................... IntroductoryRemarks. P. F. Gustafson 

## ......................... Objectives of theWorkshop. J. 

### B. Palmer 

## ...................... Engineering Considerations in theUse ofArtificial Filter Beds. 2. T. Eichards 

## .... High-Capacity Filters for Power Plant Cooling Water Intakes. 

### 9. J. Stober 

## ....... Cooling Water IntakesUtilizing Ranney Collectors or Ranney Intakes. Hydrologic Engineering Considerations for Ranney CollectorWell Intake Systems.

F. C. Mikels, T. W. Bennett 

## ..............................
N. J. Beskid 

## ..................................... iii



### An Engineering Evaluation of Porous-Dike Intake Screening Systems. J. 2. Qoberge 

## .... Biological Aspects of Porous-Dike Intake Structures. B. P. Schrader, 9. P.. Ketschke 

## . . Engineering Aspects of Passavant Screening. K. R. Siddle, R. 

### K. Sharma 

## ......... Investigationson the Protectionof Fish Larvae at Water Intakes Using Fine-Mesh

Screening. Impingement-ReleaseConcept: Laboratory Study ofa Single-Entrance, Double-Exit,Vertical Traveling Screen Concept. S. H. Maoiiente, 2. A. Tonljanovich, J. H. Heuer, S. Vigander, M. N. Smith 

## ......................... Survival of

### Dominant Estuarine Organisms Impinged on Fine-Mesh Traveling Screens

at the BarneyM. Davis Power Station. L. S. Murray, T. S. Jinnette


### .......... iv 1 3 

### 5 13


### 15
27 37 51 

### 65

69
79 

### Larval Exclusion with Woven-Slot, Fine-Mesh Screening. W. D. Cheesrnan,


### Current TVA Work on 

### the Fluid Mechanics of 

### Screens with Very Small Openings for Biological and Engineering Considerations in the Fine-Screeningof Small Organisms Investigationson the Protection of 

### Fish Larvae at Water Intakes Using Fine-Mesh

R. R. Cheesrnan 

## .................................... 89



### ...... the Exclusion of Larvae at Power Plant Cooling-Water Intakes. S. Vigandsr 

### 91


### from Cooling Water Intakes. Y. G. Mussalli, E. P. Taft, P. Hofmann 

## .......... 107 Screening. D. A. Tornljanovich, J. H. Heuer, C. W. Voigtlander 

## ............ 125 Engineering and Hydraulics of theModified Perforated-Pipe Intake. FI. T. Richards 

## ... 141 

### TheJohnson Screen forCooling Water Intakes. L. E. Cook 

## ................ 149 In-situ 

### Testing of Profile Wire Screens forLong-Term Engineering Feasibility.
A 

### Study on theProtection of Fish Larvae at Water IntakesUsing Wedge-Wire Screening. Practicalityof Profile-Wire Screen in Reducing Entrainment and Impingement.
Larval Exclusion Systems for Power Plant Cooling Water Intakes:

J. C. MiIler, K. E. Charles; T. H. Key 

## ........................ 159

. J. H. Heuer, D. 

### A. Tomljanovich 

## ............................ 169

B. N. Hanson, W. H. Bason, B. 

### E. Beitz, K. 

### E. Charles 

## ................. 195 

### Views Presented at theWorkshop. R. K. Sharrna 

## .................... 235 

### a Synthesis of

VINTRODUCTORY REMARKS Philip F. Gustafson Pivisisc 0: Environnenial im;iact SttiCier

, Arco:~:~ ::ation3 I Laborator, ?7G2 Zouth Ca;s Avenue P.rpnne, I I I inois SC’37

Within less than 

### a decade, environmental impact analysis and.pollution control have become part of our national vocabulary, and have movgd from being a more or less ad hoc art 

### to a fairly well-defined and respectable science. Concern with environmental quality--an environmental con- science, if you will--is 

### a social attitude reaching widest expression inan affluent, hightechnology society such as ours. first, until a modest degree of personal and societal well-being is reached, people are too busy with basic subsistence 

### to worry about even their immediate environment; second, there isa suspicion, which 

### is sometimes correct but often incorrect, that technology or its

### use per se isthe cause of environmental degradation. Sheer population pressure and prolonged human activityor occupation may, in and of themselves, lead 

### toprofound environmental alteration and degradation: towit, water pollution inEurope, Asia, and the Americas prior to sewage treatment practices, and the denuding of coastal areas along the Mediterranean inNorth Africa and the Middle East due to excessive timber cutting and intensive agricultural use of the land (although this effect may also have been aided and abetted by subtle large-scale climatic changes). ing, with some basis in fact, that our affluence has been gained 

### atthe expense of the environment. The reason isatleast two-fold:

In any event, there 

### is a guilt feefAfter several significant court cases, the growing attitudes of environmental concern reached fruition in this country with the passage ofFederal legislation designed to regulate emissions 

### or releases to airand water. The United Nations--through the United Nations Educational, Scientific, and Cultural Organization--took 

### a similar, though 

### less legally tough, position globally. Whereas the initial air and water quality legislation 

### was directed 

### atremedial action for existing facilities and provided a prescription or guidelines for new facilities, 

### the National Environmental Policy Act of 1969 (NEPA) required that the probable environmental impacts of a.specific action be examined before the action was taken--a look forward rather than 

### a look backward 

### atwhat had already happened. NEPA also required examination of practical 

### orfeasible alternatives for eliminatinsorminimizing unnecessary and undesirable impacts; a balancing of costs--both monetary and environmental--against the benefits, including those 

### to society as 

### a whole; and finally, 

### a disclosure of possible impacts (even of a secondary or tertiary nature) with no attempt to quantify orjudge whether they are good or bad. NEPA has been used effectively, and ithas been sadly abused. Ithas been used in the critical evaluation of nuclear power plant sites; for example, water availability for downstream communities was a major factor in the rejection of the Koshkonong site in Wisconsin. NEPA has at times tended to be used as a basis, along with airand water quality considerations, for adoption of a zero-release position which, if carried to extreme, will lead to zero-growth, 

### atleast regionally.

one hand, and the orderly continuance of our national economy--or life-style, if you will--on 

### the other. nature in terms of extremes. Thus, the attitudinal pendulum regarding concerns for the environment has, inone decade. swung from 

### a position of essentially no concern atall, to 

### a position of almost virtual overkill for protecting the

### environment from all possible impacts, and is now moving toward a more central position. Both extremes are costly interms of material and mone- tary resources (the influence of environmental protection on inflation is presently a subject of heated debate). Clearly there isa need for

### a reasonable balance between protection of the environment, on Itseems part of human nature to regard matters of a societal or sociopolitical

A balanced or middle-of-the-road position isbeing achieved, albeit somewhat tortuously, through thejudicial system and the public hearing process, along with a certain amount of 

### just plain common sense. As a result of these processes, technical problems have been identified, and solutions or remedial procedures in many cases have been developed. Generally, this has

1been a healthy interactive relationshipand one which has shown that often the proper applicationofexisting or new technologies can, infact, solve problems due totechnology inthe first

. place. Overall, this has ledto environmental improvements accompanied by increasedapplication of technology--primarily, inthe cases considered here, the production of increasedquantities ofelectric power. This workshop isa direct outgrowth of the continuing effort to strike a reasonable balance between energy needs and environmental protectionmentioned above. that the cooling-water intake end of the system (the steam power plant inthis case) had the potential to ingest and destroy biota tothe detriment of the adjacent ecosystem. Indeed, a power plant may be thought of as a man-made predator, often of appreciable magnitude. the strong features of impact assessment isto identify possible problems or problem areas, and to indicate the need for Research & Development tofill a knowledge gap or to correct an undesirable situation (a fact that isoften overlooked). Fish impingement and larval entrainment isan excellent example of biological research and engineering development working hand-in-hand to eliminate orminimize a problem, real or potential, inan effective, publicly acceptable manner. Early on, itwas recognized
One of

The contributors attheworkshop described arid discussed, indetail, the theory and design of various systems and schemes employed to reduce larval entrainment, and, where possible, the real-world success ofthese methods as judged by operating experience. Whereas procedures to reduce impingement may have littleeffect on larval entrainment, the converse isone inwhich both are reduced--i.e., reducing entrainment by diversion, velocity-reduction, or fine-screening techniques essentially eliminates impingement, if done wisely and properly. these investigationswill be of directvalue tothose designing new facilities and upgrading present ones, as well as tothose engaged inenvironmental impact analysis, 316(b) demonstration efforts, and likematters. The results ofOBJECTIVES OF THE WORKSHOP
John B. Palmer Research 8 Development Southern California Edison Company P. 0. Box 800 Rosemead, California 91770

The objectives of this workshop are based on two aspects of today's electric utilityindustry. research can be incorporated intothe design of specific power systems. This potential for incorporation ismade possible by an explicit corporate commitment to natural resource conservation--a commitment which issupported by the utilityrate base, as isnow the case in California. The second underlyingaspect isthe necessity for long-range planningwithin the utility industry. abilityofthe information necessary formaking decisions which will permit those goals to be achieved

## . The first isprovision that environmental design criteria developed through responsible

Planning ispossible only inan atmosphere ofwell-defined goals and availInthe papers presented atthis workshop we look beyond minimizing adult losses, and we review the state of information on intake designs which have the potential for excluding the smaller lifestages ofaquatic organisms: Itseems likelythat planningfor future utilitygenerating capacity will involvedecisions as to whether or not larval exclusion capability isa viable design feature of power plant cooling water intake systems. 

### In thisworkshop, the hardware end of this problem isaddressed: Are such things feasible at all and, ifso, under what conditions are they reliable, atwhat costs, and with what degree of biotic protection? eggs, larvae, and juveniles.

The charter for thisworkshop reads as follows: The aim of the workshop isto reach an evaluation of the status of various design concepts which could exclude the meroplanktonic larvae orjuveniles of fishand invertebrates from the cooling water of steam electric power stations. the possible domain ofapplicability for each concept (coastal, estuarine, riverine, lentic; once-through or off-stream) and the status ofcurrent research todetermine engineering and biological effectiveness. neeringaspects which requirefurther research inorder to bring all concepts on a par by, say, 1983; so atthat time the power industrywill be able todetermine ifthere exist best technology options inthis general area. The papers presented are publishedas the Proceedings of thisWorkshop. We plan to explore

For those concepts which have promise, we intend to identify biological or engiInthe summary we have incorporated the consensus of the participants as towhere research and development inthis area stands and where itought tobe directed. this field presented a paper atthis workshop. discussions, and we have incorporated several ofthese valuable comments inthe proceedings.
the nextseveral years. We realize that not everyone who isactive in However, all those present contributedtothe
Itseems likely that research and development inthis area will proceed ata good pace over If this proves tobe the case, we plan to reconvene inabout two years.

3ENGINEERING CONSIDERATIONS IN THE USE OF ARTIFICIAL FILTER 

### BEDS
Richard T. Richards

INTRODUCTION The artificial filter bed isone of several water screening methods proposed to eliminate or reduce the entrainnieni of small aquatic organisms in the cooling water supplied to power plants. I say "proposed" because 

### its actual power plant use has been minimal to date. The engineering problems involved in developing an intake filterof high reliabilityand large capacity are formidable and as yet largely unresolved. This discussion isa brief review of some of these problems, and isgenerally related to the development of a filterintake forone specific, reasonably favorable 1ocation. Entrainment is a growing concern because of the large volumes of water withdrawn from our water sources for power plant cooling, including withdrawal of makeup water for coolingtowers. Although the water requirements areno more than about 

### 5' of once-through cooling, itcan be assumed that all entrained organisms will be destroyed inthe cooling tower cycle. On 

### the other hand, continuing biological studies indicate that a large proportion of 

### the organisms entrained inthe once-through cooling flow may well 

### survive. From a practical standpointwe should con- centrate present research efforts on developing a filter suitable formakeup flows in

### the range of 0.6 m3/s (10.000 gpm) to about 3.1 

### m3/s (50,000 gpm). 

### The problems in that range areenough of a challengewithout considering the artificial filtering of once-through cooling water flows in the range of 12.6 to 63 m3/s (200,000 to 1,000,000 gpm).
HISTORICAL NOTES 

### For many years artificial filters have been used for small water supply withdrawals. primary purpose has been 

### toproduce a well-filtered water rather than to protect aquaticorgan.- 

### isms from damage. suspended sediiiients and algae growth are low. 

### The A few of these filtershave been successful, usually inwaterswhere the Many have been failures.

56
The subject of filters for power plant use was discussed intwo papers atthe Second Workshop on Entrainment and Intake Screening in 1973. At that workshop Stober’ covered the details of a test filter design for a salt-water environment. neering design concept fora very large filter applicable to a once-through system. Strandberg’ presented a paper on an engiOne recent attempt to use an artificial filter for power plant makeup water ended inabandonment of the filterafter construction, and itsreplacement with a perforated-pipe intake. This filterwas designed for a Z.0-m3/s (33,000-gpm) flow, typical of the capacity we are considering here. for the Montour Steam Electric Station of the Pennsylvania Power and Light 

### CO.~Several field modificationswere made inthe original design, but ultimately itcould not be prevented from clogging ata rate considered unacceptable. Itwas placed on the west branch of the Susquenhanna River todraw makeup water

THE ARTIFICIAL FILTER Figure 1 

### is a schematic drawing of an artificial filter. An area isexcavated and backFor the periodic removal of undesirable filledwith a specially graded filtermedium. filteredwater and carries itto the pump structure. material which has settledout on the bed, water and/or airmay be backwashed through the collector pipe or through separate pipes. Figure 1, or inconcrete box units, removable wire basket units, etc. A perforated pipe under this filter collects the
The filtercould be ina simple excavation, as shown in

WATER BACKWASH

### PIPE

RATED COLLECTOR AIR BACKWASH 

### PIPE
Fig. 1. Schematic ofArtificial Filter

The filter itselfmust be a very carefully graded material (sand, stone, and possibly other Itmust additives) ofa certainarea and depth to meet the filtering criteria for a given site. also be protected from scouring.
GENERAL DESIGN CRITERIA Power plant coolingwater supply requirements are particularly stringent. With a oncethrough cooling system, the plant cannot operate even for minutes without a coolingwater supply. This means a system that must operate 24 hours a day, 7 days a week for 30 or 40 years. not be shut down for normal maintenance unless duplicate facilities are provided. are nearly as stringent for cooling tower makeup supply. tothe towers., there isenough water storage capacity inthe coolingtower basins topermit a water supply shutdown ofonly one half toone hour. Unless there 

### is a storage pond or lake associatedwith the cooling tower system (a relatively rare provision), the requirement for makeup water 

### is essentially continuous. ItcanThe criteria If the makeup water 

### is going directly

Power plant shutdown due toa coolingwater interruption could cost inthe range of $200,000 per day fora 400-MWe unit.7
The criteria fora filterdesign include the following items: Reliability. The facility

### must be capable offunctioning at full output for

### the lifeof the plant. Operability. Maintainability. Operation 

### must be possible with reasonable operator attention. There must be duplicate filtersto permit backwash, and 

### there must be Implied accessibility formaintaining the filterbeds (periodicreplacement or rebuilding). here too isthe necessity for providing a facility that does not require excessivemaintenance. Environmental Acceptability. 

### The facility

### must be environmentally acceptable. For example, the turbidity during backwash may have to

### meet certain stringent standards, 

### as in

### the example described in 

### the next section. Reasonable Costs. Thismay be a sensitive subject

### where the environment 

### is involved, but it

### is nonetheless an important factorwhich ultimately will determine whether 

### the filter system isto be used.
ENGINEERING ASPECTS OF A TYPICAL FILTER DESIGN 

### In 1972 a filterdesign 

### was prepared and submitted to regulatory authorities inconnection with the makeup water system forNuclear Project #2of the Washington Public Power Supply System (WPPSS-2) on the Columbia River. The WPPSS-2 facilitywas designed to handle a maximum flow of 1.6 

### m3/s (25,000 gpm). A pumping station 

### pumps the water tocooling tower basins about three miles from 

### the river. There 

### is no storage capacity at

### the power plant siteexcept in

### the cooling tower basins themselves. Several filterconcepts were studied, including a filter placed directly inthe bed of the river, an infiltration gallery inthe riverbank, and a filterplaced in

### the bed of an artificial off-stream channel. The final selection, shown 

### in

### Figure 2, was a system of seven offstream individual filter

### unitscontained by sheet piling and preceded by a river diversion system and a stillingbasin. successfully, but that certain major research (described 

### inResearch Needed) would be 

### required for a final design. perforated-pipe intake described inReference 4. 

### Itwas concluded that 

### the filterconcept could be developed Ultimately, the filterconcept was set aside 

### infavor of themodified

.-c-- ,360

0



### 0 50 100 

### 200 300 

# -

SCALE IN 

### FEET

Fig. 2. Schematic of Proposed Artificial Filter Facility8
Itcan readily be seen that the artificialfiltersystem selectedwould have been a very complex facility. The system might have become even more complex if proposed model and field studies had dictated changes inthe design. lightedas we discuss the passage ofwater from the river tothe filterand back to the river, through the various components ofsuch a system. Engineering factors and problems will be highDiversionWall. A riverdiversionwall, to be developed inpart by model tests, would direct water intothe channel insufficient quantity for proper performance not only of the intake but ofthe backwash system. back to the river. Backwash requires a continuous flow across the filter and
Flow Control Structure. A sheet pilechannel would extend from the riverdiversion wall to a flow control structure atthe head of twin stillingbasins, shown in Figure 3: The flow control structure was required to limitthe inflowtothe proper volume for intake and backwash and topermit diversion offlow to either or both stillingbasins. abilitywere factors which dictated the sheet pilechannel sidewalls. Channel velocity would be limited to an average of 1 m/s (3 fps) to avoid bottom erosion, as determined by a study of the characteristics ofthe bottom material. Bank stability and maintainPLAN

EL354 GRADE MANUAL GATEOPERATORS



## 1 4FLUSH BOTTOM 

# /- 22' 

### ' 22'L-i SLIDE GATES 

# I

SECTION A-A Fig. 3. Schematic of Flow Control Structure9 

### StillingBasins. the river suspended sediment, 

### thus taking the burden off the filters. lated and dredged while the other continued to operate. a relatively clean river. use of such an artificial filter. ities

### were determined by the settling rate of the sediment tobe removed under the 

### worst river conditions. periods of high level water. would reduce filterperformance. by 9.1 

### m (19 ftby 30 ft)as shown schedmatically inFigure 4. 

### ters were studied 

### in detail and a design developed as far 

### as possible without the final mode'l and prototype field tests. The complexity of water piping required is shown in Figure Q. additional airbackwash piping isnot 

### shown atall inthe plan. The typical filterbed shown in Figure 

### 4 

### is approximately 

### 2 

### m (6 ft)deep, and 

### is 

### tobe covered by a 

### minimum depth of 0.6 

### m (2 ft)of water. Stilling (sedimentation) basins would settle

### cut asmuch as possible of 

### One basin could be isoItshould be noted that 

### the Columbia is The length of the stillingbasins and the flow-through veloc

### Even modest seasonal sediment could be a major factor 

### ruling out the
The basins were to be protected by dikes which would prevent flooding during Periodic flooding of the facility, with attendant sediment loads,
FilterBeds. A filterbed array would consist of seven separate filtercells, each 5.8 

### m Fine- and coarse-textured filThe

Distribution Structure. 

### A distribution structure would be required 

### to isolate the seven filter sections for operation, backwash, and maintenance, and is shown conceptually inFigure 5. Road System. Not shown 

### inthe figures isthe road system to permit access 

### to both the stilling basin and 

### the filtersystem for trucks, cranes, and othermaintenance equipment. Material periodically dredged from the stillingbasins would be disposed of on land. necessary auxiliary features would add considerably to the cost of the filterintake facility. Enough water flow 

### must be maintained across the filterto carry the backwashed material downstream. sented a major problem 

### inthat the limitations on raising river turbidity were very stringent. The regulatory authorities limited 

### the increase to five Jackson Turbidity Units (JTU) above the natural river turbidity 

### atany river stage. flow over 

### the filterhad tobe sufficient to keep theclarity of 

### the water reentering the river 

### within the sDecified limits. Preliminary oDeratins studies called for continuous operation of Such
Backwash. Backwash 

### is achieved by airflow up through the filter bed. This pre- (Normal river turbidity 

### is about six JTU.) The
the systemwith five filter

### units delivekngwater-and two filter Return Channel. The final element inthe filterfacility is 

### river.
RESEARCH NEEDED A major model and field testina Droqram 

### is required to final units being backwashed. the return channel to the

ze the desisn details of such a fi1,teriystem. several hundred thousand dollars. For this particular project no 

### tests were undertaken because an alternative perforated-pipe intake4

### was adopted before the filtertesting program could be initiated; however, the following testswere 

### among those recommended:
suitable gradation of filtermaterial, test the rate of clogging, and perfect the backwash sys

### tem. Columbia River water 

### must be 

### used and the temporary laboratory facility

### must therefore be located near 

### the siteof the intake. Sound indicates the complexity of such an installation.] It should be noted, however, that the salt-water environment of Puget Sound imposes more biological fouling problems than would be expected forColumbia River fresh water. Itis quite possi6le 

### thatthe expense of this program would-be inthe order of



# - An on-site laboratory 

### test of one ormore short sections of the filterbed to develop 

### a
Stober's description of a similar test facility inPuget



# - An extended field test of a prototype filter section inthe 

### river, located such that the characteristics of the test unitwould duplicate those of the final installation. This test should be run for all river stagestoassess the influence of actual river conditions on the performance of 

### the filterbed. backwash, and monitoring facilities. The 

### test facility

### must be complete with appropriate pumping, air



# - A reduced-scale laboratorymodel test of the entire filtercomplex (approach channel, sedimentation basin, etc.) and asmuch of the Columbia River as isnecessary to accurately simulatethe filtersystementrance and exit conditions. This model isessential to determine theoptimum angle of channel approach and the proper orientation and length of the river diversion wall and to refine some of the detailsof the gate structure. testing of thismodel, extensivefieldwork must be done to determine the river physical and flow characteristics foraccuratemodeling. Model verification will be required to assure that the model does infact duplicate the actual river flow conditions atthe intake site. Prior to construction and

## .... 

# I

. CAPACITY(ISPARE) 

## I

# II ---

### -

# t---

# -=$

I I

PLAN 

# -

3-18"PPERF. 

# IM

MIN.W.L.EL.3437

# I

# l+l I

STONE FII

SECTION 

### 6-B :T PILING

Fig. 4. Sketch of FilterBed and Typical FilterCell11



# +‘ (D 

### cu 

# 0’: P ’, -



### PLAN

SECTION

Fig. 5. Schematic of Distribution Structure



### CONCLUSION We can see from thisdiscussion how the simple filter concept illustrated in Figure 1 can grow into a relatively monstrous project from an engineering standpoint. Although some aspects of filter systems might be refined and used as standards 

### atsome future date, the majority of filterengineering will be site-related and will require a new design for each project. If the intake is 

### to have the high degree of reliability required of a power plant installation, the engineering of 

### an acceptable artificial filter system will continue to be difficult and costly-12
REFERENCES 1. Stober, Q- J., C. H. Hanson, and P. B. Swierkowski. 1974. A high capacity sand filter for thermal power plant cooling water intakes. Part I: Model studies and fouling control techniques, pp. 317-334. Entrainment and Intake Screening, 

### The Johns Hopkins University, Baltimore, Md., Feb. 5-9, 1973. EPRI Publ. 

### No. 74-049-00-5. Electric Power Research Institute, Palo Alto, Calif. 2. Strandberg, H. V. 1974. A high capacity.sand filterforthermal power plant cooling water intakes. Part 11: Design concept, pp. 335-343. In 

### L. D. 

### Jensen (ed.), Proceedings of the Second Workshop on Entrainment and Intake Screening, The Johns Hopkins University, Baltimore, Md., Feb. 5-9, 1973. EPRI Publ. 

### No. 74-049-00-5. Electric Power Research Institute, Palo Alto, Calif. L. D, Jensen (ed.), Proceedings of the Second Workshop on

3. Metzger, A. W., and F. J. Sawicki. 1974. Mountour Steam 

### Electric Station Alternate 

### River IntakeSlotted Pipe Installation. Structures and Hydraulics Committee 

### Winter Meeting, Feb., 1974.
tion. J. Hydraul. 

### Div. Proc. 

### Am. Soc.

### ‘Civ. Eng. 102:139-149. Paper presented atthe Pennsylvania Electric Association
4. Richards, R. T., and M. 

### J. Hroncich. 1976. Perforated-pipe water intake for

### fish protec-HIGH-CAPACITY FILTERS FOR POWER PLANT COOLING WATER INTAKES
Quentin J. Stober FisheriesResearch Institute

University of kashinofon Seattle, tiashincton 98195

SUMMARY A high-capacity model filterwas tested as a method of preventing the entrainment and impingement ofpelagic eggs and larval fishes at power plant intakes. proposed plant site inPuget Sound. engineeringdesign concept developed and reported by Stober et al. (1974) and Strandberg (1974) were reviewed. Tests were conducted ata Model filterstudies, fouling control techniques, and an

The hydraulic considerationsof seawater filtration through an anthracite-gravel filter indicatedthat the size ofthe anthracitemedia should range from 2.4 to 7.9 mm with the optimum from 3.2 to6.4 mm. 712.7 Lpm/m2 toachieve the desired filter bed expansion of 252.
and 407.3 Lpm/m2, were not observed to affect the horizontal or vertical mobility ofjuvenile fishes or invertebrates even above the filter surface. larval stages of marine fouling organisms, was not practical. The coarseness of the media was restricted by the design backwash rate of
Filterflow velocities of 0.305 to 0.610 cm/s, which related tofiltration rates of 203.6 The exclusion of plankton, including the
The seasonal changes inwater quality (turbidity, temperature and salinity) were determined on-site. Turbidity was subject toseasonal variations, due primarily to planktonic organisms (1-3 FTU) and tosuspended sediment (3-6.5 FTU) from winter and spring flooding of the Skagit River, Suspended sediment caused the greatest short-term reduction infilter performance. A filtration rate of 244.4 Lpm/m2 through the 2.32-m2 model yielded a mean volume of over 9462.5 m3 per run. ranged from 5.4 to20 days, depending on influent turbidity. selected was 305.5 Lpm/m2 through an active filter area of8361 

### m2, divided into seven units to yield a coolingwater output of 42.5 m3/s. anoxia, single-dose chlorination, heat treatment, chlorination and heat treatment during backwash, and daily two-hour chlorination. Based on barnacle abundance and growth rates, the most effective fouling control techniques tested were backwashing with heated seawater, daily chlorination, and anoxia. The mean run time was 260 hr to a head loss of 1.32 m. Filtrationtime The design filtration rate

Sixmarine fouling control techniques were tested, including backwash with ambient seawater,

The test data were utilized inthe development ofthe engineering design concept, including siting and operational procedures. Additional on-site model testingover one annual cyclewas recommended toprovide operating experience priorto final design; however, such tests were not conducted due to cancellation ofplans tobuildthe proposed power plant. The concept of filter intake systems toprevententrainment of aquatic organisms has been evaluatedmore frequently inriverenvironments (DeVries 1773; Richards 1978). River water is characteristically loadedwith large amounts of suspended particleswhich greatly reduce the performance and reliabilityofsand filtersystems. Operation inother environments where the concentration of suspended sediment isusually less may be more promising (i.e. lakes, reservoirs, o'ffshore marine environments); however, biological fouling isan additional problem in marine environments. -\ Filter intake systems could be a very attractive and effective technology for the exclusion Extensive biological and engineering research of Pelagic eggs and larval fishes. developed toallow reliabledesign and operation. However, the present technology isnot sufficiently

1314
and development programs designed tomeet site-specific criteria are needed ifthis technology isto be feasible. short term. Application ofalternate technologies may be more cost-effective inthe

REFERENCES DeVries, J. 

### J., R. B. Krone, and J. Amorocho. 1973. Sand Filters for Screening atWater Diversions: A Feasibility Study. Water Science and Engineering Paper 

### No. 1053. Department ofWater Science and Engineering and Department of Civil Engineering, University of California, Davis. 48 pp. Richards, R. T. 1978. Engineering considerations inthe use o f a r t i f i c i a l filterbeds, pp. 5-12. InR. K. Sharma and J. B. Palmer (eds.), Larval ExclusionSystems for Power Plant CoolingWater Intakes, Proceedings ofthe Workshop held at Shelter Island Inn, San Diego, Calif., Feb. 7-8, 1978. Stober, Q. J., C. H. Hanson, and P. 

### B. Swierkowski. 1974. A high capacity sand filterfor thermal power plant cooling water intakes. Part I: Model studies and fouling control techniques, pp. 317-334. Intake Screening Workshop, The Johns Hopkins University, Baltimore, Md., Feb. 5-9, 1973. EPRI Publ. 

### No. 74-049-00-5. Electric Power Research Institute, Palo Alto, Calif. Strandberg, H. V. 1974. A highcapacity sand filterfor thermal power plant coolingwater NUREG/CP-002. Argonne National Laboratory, Argonne, Ill.



### L. D. Jensen (ed.), Proceedings ofthe Second Entrainment and

intakes Part 11: Design concept, pp. 335-343. 

## & L. D. Jensen (ed.), Proceedings ofthe Second Entrainment and Intake Screening Workshop, The Johns Hopkins University, Baltimore, Md., Feb. 5-9, 1973. EPRI Publ. No. 74-049-00-5. Electric Power Research Institute, Palo Alto, Calif.COOLING WATER INTAKES UTILIZING RANNEY COLLECTORS OR RANNEY INTAKES
Frederick C. Mikels Ranney Method Western Corporation Kennewick, Washington 99336 BOX 6387

Truman W. Bennett The Ranney Company Box I45 Westerville, Ohio 43081

Abstract Minimization of the loss of aquatic biota isa major factor inthe locaiion, design, construction, and capacity of cooling water intake structures. In a comprehensive report, the U. S. Environmental ProtectionAgency (1976) has reviewed the present methods and-technology available for minimizing adverse environmental impact of coolingwafer intakes. Two types of intakes, described inthe report and classifiedas non-conventional intakes, are discussed inthis paper: the Ranney Collector, which is a subsurface intake utilizingnatural sand and gravel deposits totransmit water from a surface source, and the Ranney Surface Water intake, which isa submerged, horizontal perforated-pipe intake.

INTRODUCTION Where proper geological conditionsexist, Ranney Collectors afford a means of screening large volumes of naturally filtered surface water by inducing infiltration through existing sand and gravel deposits. that neither impingement nor entrainment oflarval fish or drifting river organisms occurs. The water filtered isfree of turbidity, suspended matter, organic matter, and pathogenic bacteria and has a mineral quality very similar to that of the surface source. Water temperatures have a seasonal variation similar to that of the surface source, but significantly 

### less inmagnitude. Ranney Collector systems 

### have been designed for capacities up to 340,000 m3/day.


### tor, is

### not dependent upon natural sand and gravel deposits and can be used inalmost any 

### surface source. The Ranney Intake consists of offshore horizontal perforated-pipe screens, connected toan onshore pumping station. Maintenance isminimal, since there are no moving parts and the screensare normally self-cleaning. to 650,000 m3/day. 

### The screening and filteringcharacteristics of Ranney Collectors are such

The Ranney SurfaceWater Intake, based upon 

### the same design concepts as the Ranney CollecRanney Intakes have been designed for capacities up

THE RANNEY COLLECTOR INDUCED INFILTRATION Thevalleys of most major streams and 

### rivers of the United States are underlain by unconNormally, these aquifers are saturated with solidated alluvial deposits of sand, grave’l, clay, and 

### silt. Inmost instances, these deposits are porous and permeable and are called aquifer-s. water toa level ator near the level ofthe surface stream 

### orriver. Under natural conditions of thehydrologic cycle, the water table in the aquifer slopes toward the river, and groundwater isslowly moving toward and discharging into the river. During periods of high river flow the
1516 hydraulic gradient may temporarily be reversed and water from the river will discharge into the aquifer. Thus, 

### a free interchange of surface water and groundwater occurs continuously, on a natural, cyclic basis. If the water level in the aquifer 

### is lowered by pumping below that of 

### the river, a hydrauThe cone of depression created by 

### the pumping will continue 

### to expand until licgradient will be created, causing water 

### toflow from the river into the aquifer and 

### tothe source of pumping. a steady-state flow condition exists in which most of the water pumped will come from the 

### surface source. This process iscalled induced recharge or induced infiltration.

I The process of induced infiltration assures a permanent, dependable 

### water supply, since it derives water from a known, definable surface source and 

### is not dependent upon recharge from seasonal rainfall distribution. In effect, sand and gravel aquifers, as they exist in nature, perform as high'ly effective screening and filteringmechanisms, resulting in

### the production of 

### a clean, potable water which farexceeds the requirements for cooling water supplies.
HYDROGEOLOGICAL INVESTIGATIONS The principles and theory of induced infiltrat Kazmann 

### (1 947, 1948, 1972), Rorabaugh (1 952, 1956), briefly discussed here. The prime requisite for an 

### a permeable sand and gravel aquiferwhich ishydrau as a stream, river, or lake. 

### on have been extensively documented by Walton (1970), and others and will be only infiltrated water supply isthe existence of icallyconnected with a surface source such
Atany given site, the magnitude of the water supply thatcan be developed by induced infiltration isa function of the following independent variables: thickness of the aquifer, the permeability of the aquifer, 

### the infiltration rate of the riverbed intake area, and the type of structure tobe used 

### toproduce the water. A thorough hydrogeological investigation isnecessary for evaluation of these variables and design of the structures prior to the actual construction of the water supply installation. Initially, such an investigation consists of the drilling and sampling of a series of exploratory test holes along the riverbank to determine the depth, zharacter, saturated thickness, and areal extent of the aquifer. These test holes are drilled until 

### the base of the aquifer is reached, generally represented by a layer of impermeable material such as clay or bedrock. At sites selected from the results of the exploratory test drilling, detailed pumping tests are conducted. the depth and saturated

The pumping test requires the construction of 

### a pumping well and 

### a series of properly The pumping well ispumped continuously, 

### at

### a constant rate, until spaced observation wells. water levels become stable and a steady-state condition exists. levels in

### the observation wells and changes in

### river stage are continuously recorded. Experi- ence shows that the duration of such a pumping test should be 

### not less than 48 hours and, in some instances, as long as 96 hours. The data from the pumping test are used todetermine the permeability of the aquifer and the infiltration rate of the riverbed. With this information, thequantity and quality of 

### water that can be produced by induced infiltration can be accurately predicted. During the test pumping, water



### Over the past 35 years, 

### ourcompanies have carried out more than 300 such hydrogeological investigations. A comparison of predicted results with actual results shows thatpumping test methods are extremely reliable in predicting water supply developments by induced infiltration. According 

### toMikels and Klaer (1956), an accuracy ofestimates of 10 to 15 percent can be normally expected when applying these methods. 

### Thus, infiltrated water supplies can be designed with the same degree of predictability 

### asany other type of water supply development.
METHODS OF DEVELOPMENT The principal methods of developing infiltrated water supplies are vertical wells, infiltration galleries, and Ranney Collectors. of initial cost, operation, maintenance, and reliability. Each method has advantages and disadvantages interms
Vertical wells can penetrate the entiredepth of the aquifer and have been used successfully to induce infiltration inmany localities inthe United States, particularly along major rivers and streams. When water requirements are small, the initial cost of a vertical well system is often lower than othermethods. However, a major disadvantage of a vertical well system is that insufficient screen area is exposed to the aquifer, due tovertical limitations of the aquifer. high frictional orwell losses. amount of induced infiltration possible. ated well loss may create clogging or incrustation of the well screen, materially reducing the lifeof the well.Thislack of screen area results in high entrance velocities and, consequently, These losses'reduce theamount of usable drawdown and limit the Furthermore, the high entrance velocities and associ-17
Since the depth of the alluvial aquifers along most rivers of the United States isgenerally 

### less than 20 m, the capacityof a single vertical well can 

### be expected to be on 

### the order of 6,000 m3 per day. Thus, for 

### a typical nuclear power plant, consisting of two 1300-MWe units and having 

### a cooling water makeup requirement of 200,000 m3/day, over 30 vertical 

### wells would be required. pipelines would render such a system economically impractical, not only in

### terms of initial construction costs but also in terms of operation and maintenance costs. well systems have been proven practical for smaller water supplies, it

### is doubtful that they represent a viab’le alternative formost large cooling water supplies.
from 

### the ancient times of Persia and the days of early Greece. zontal, permeable conduits or pipes constructed inunconsolidated materials below the water table. Because of the large area of screen exposed 

### tothe aquifer, infiltration galleries are more efficient and generallycollectmore water than vertical wells. results inlow entrance velocities and minimal well losses, resulting 

### in

### a structure relatively free from clogging and with 

### a long life. 

### Los Angeles, California, and Des Moines, Iowa, which have been 

### used for over 40 years without reported reduction incollection rates. Stone (1954) also reports yields of up 

### to50,000 rn3/day for a single infiltration gallery. because construction isby open excavation below the water table, 

### its application is*limitedto very shallow depths, generally not in excess of 6 m. The multiplicity of pumps, pumphouses, electrical connections, and interconnecting Thus, while vertical

Infiltrationgalleries are among the oldest known means of inducing infiltration, dating Infiltration galleries are hori
### This large screen area Stone (1954) cites examples of galleries 

### at
The chief disadvantage of 

### an infiltration gallery 

### is that,



### A relatively new method ofdeveloping water supplies by induced infiltration isthe Ranney Collector, developed by Leo Ranney of Northwestern University inthe early 1930’s. The Ranney Collector combines the major advantages of both vertical wells and infiltrationgalleries, since 

### itpermits utilizing the entire depth of 

### the aquifer and allows virtually unlimited amounts of screen 

### tobe exposed to the aquifer.
RANNEY COLLECTOR DESCRIPTION Figure 1 isa sketch of 

### a typical Ranney Collector. A large-diameter reinforced concrete caisson issunk, by open excavation, to the base of a sand and gravel aquifer adjacent toa surface source. The bottom of the caisson 

### is sealed with a concrete plug and, near the base of the caisson, horizontal screen pipes are projected radially, much like the spokes of a wheel. These horizontal screens are projected by 

### a combination washing and jacking process, resulting inthe removal of large volumes of fine material and the development of a natural gravel zone surroundingthe entire length of each horizontal screen lateral. Silitch (1948) states that from 0.3 to 0.6 m3 of finematerials are removed foreach 

### meter of screen pipe projected, resulting in a 

### natural gravel bed ofmore than 1.2 

### rn indiameter surrounding the screen pipe. extended above flood level to form a base for 

### a pumphouse and pumps, resulting ina complete water-producing system contained inone 

### unit. The Ranney Collector 

### is inreality a special type of infiltration gallery that can be economically constructed to depths of up to 60 m. large area of horizontal screen, surrounded by highly permeable gravel, tothe aquifer. results invery highyields, while maintaining extremely lowentrance velocities. entrance velocities virtually eliminatewell 

### loss, clogging, and incrustation, 

### thus assuring a reliableand long-lived installation.
thicknesses of 450 to 600 rnm. The horizontal screen laterals are fabricated from heavy steel plate orpipe, withlongitudinal keystone slots, and may range from 200 

### to 600 

### mm indiameter. 

### As much as 600 m of horizontal screen pipe have been projected in some Ranney Collectors, with individual laterals ranging up to 135m inlength. 

### Atthepresent time, there are more than 300 Ranney Collectors inoperation intheUnited Theyields.of Ranney Collectors range up’to as Some of thelarger Ranney Collector systems The caisson 

### is

The basic principle consists of exposing a This These low

The size of the reinforced concrete caissons ranges from 4 to 6 

### m indiameter withwall

States and Europe. industrial process and cooling water supplies. high as 80,000 m3/day from a single installation. 

### are the Grand Gulf Nuclear Station (120,000 m3/day), the Indiana Ordnance Works (250,000 m3/day), the Wabash 

### River Ordnance Works (340,000 m3/day), theSonoma County, California, Water Agency (250,000 m3/day), and Belgrade, Yugoslavia (300,000 m3/day). yield capability required for large power plant cooling water supplies. About 55:, 

### of these aremunicipal 

### water supplies, while the remaining 45%are

Thus, Ranney Collectors have the

SCREENING AND FILTERING CHARACTERISTICS Klaer (1953) statesthat experience has shown that turbidity, suspended matter, organic matter, and pathogenic bacteria are removed from water by induced infiltration, especially in

### Fig. 

### 1. Sketch of Typical Ranney Collector

the use of Ranney Collectors. river, which 

### is comparable 

### inmany ways to a very large slow sand filter, but larger and thicker than any made by man. have been computed using themethods of Walton (1970) and are given 

### inTable 

### 1. These riverbed infiltration rates are very low, averaging only 0.0023 

### cm/s, and the filterbed thicknesses (or aquifers) are very large, ranging from 4.4 to 22.0 

### m. man-ma.de rapid sand filter has an infiltration rate of 0.27 cmfs, orover 100 times fasterthan 

### the riverbed infiltration rates, and a filterbed thickness of only about 1 m. Velocities through theriverbed are also-given inTable 1; the average 

### is only 0.0078 cm/s. 

### These velocities areextremely low and areonly about one-two thousandth of the intake velocity of 15

### cm/s, generally considered adequate 

### to prevent impingement of adult and most juvenile fish (Schreiber 

### etal. 

### 1973). As a matter of fact, 

### the riverbed velocities are 

### so low, being inthe range of natural seepage, that even impingement of larval fish or free-floating river organisms would not be expected to occur. pathogenic bacteria, which vary in

### size from 1 to 4 U, itislikely that no entrainment of larval fish or free-floating river organisms will occur. The filtering abilityof the riverbed isfurther shown by thelow turbidity measurements (Table 1). than 1.0 JTU and most show a turbidity of less than 0.5 JTU. sing a proposed Ranney Collector system for a nuc?ear power plant in western Washington, state that the utilization of a subsurface intake system will prevent any damage to the river's aquatic life and have littleimpact upon the land surface 

### attheintake area along theriverbank. 

### This screening and filtration takes place on the bed of the Riverbed infiltration rates for a number of existing Ranney Collectors
As a matter of comparison, a conventional

Furthermore, since riverbed infiltration 

### is known to filter

Turbidity removal 

### is virtua1ly.complete; all installations show a turbidity of less Kenny and Wise (19751, in discusWATER QUALITY AND TEMPERATURE The water from Ranney Collectors, being naturally filtered, 

### is clear and free of turbidity, suspended matter, organic matter, and pathogenic bacteria. After a relatively short period of19
Table 1

# - Screening and 

### Filtering Characteristics of Ranney Collectors Velocity Ranney Collector Below River 

### Ranney River Infi1 tration Riverbed Riverbed Through Turbidity (JTU) Aqilifer Depth Site Level (m)a Collector Maximum Rate (un/s.)b (cm/s) Boardman, Oreg. 71.5 0.40 29 8.7 10-4 Carmichael, Calif. 6.6 0.10 55 1.6 10-3 Charleston, Ind. 15.2 

### - - 1.6 10-4 Crescent City, Calif. 4.4 0.35 200 9.3 10-3 Gladstone, Oreg. 8.0 0.45 

### - 1.4 10-3 Kalama, Wash. 8.0 0.40 100 4.3 x 10-4

Collectors 

### 1, 2, 3 9.1 0.40 29 

### 2.2 10-4 Kennewick, Wash.

Collector

### 4 10.4 0.11 29 

# - Collector 5 8.5 0.03 29 

### - Marysvi

### 11 e, Wash. 10.0 0.80 29 5.6 10-3 Port Angeles, Wash. 15.5 0.50 35 7.6 10-4 Sacramento, Calif. 22.0 0.11 170 2.6 10-3 

### St. Helens, Oreg. 10.5 0.33 29 1.1 10-4

Collectors 

### 1 & 2 21.0 

### 0.10 1520 2.3 x,10-3 Collectors 3 & 4 

### 20.1 0.23 1520 2.3 10-3 Woodland, Wash. 6.0 0.11 5.0 10-3 Sonoma Co., Calif.

aTo convert meters tofeet, multiply by 3.2808. bTo convert centimeters per second to feet per minute, multiply by 1.9685. 2.9 10-3 5.4 10-3 5.4 10-4
4.7 10-3 1.4 10-3 3.1 10-2

7.2 10-4


### - - 1.9 10-2 2.5 10-3 8.7 10-3 3.6 x 10-4
7.9 10-3 7.9 10-3 1.7 x lob2

pumping, 

### themineral quality of the water will approach 

### the average mineral quality of the surface source, butwill generally be slightlymore mineralized due to small water contributions from groundwater

# - Theis (1941) has developed equations for determining the percentage ofpumped water being diverted from a surface source of recharge. For a well or Ranney Collector located 

### on the river's edge near the source 

### of recharge, computations from 

### these equations indicate that over 90%of 

### the water pumped 

### is diverted from the river after

### a relatively snort period of pumping. 

### As 

### a confirmation of this, riverwater percentages have been determined for a number of existing Ranney Collectors, based upon water quality data, and are given 

### inTable 2. selected as the mineral parameter for 

### these determinations because of 

### its stability 

### in solution. 

### The percentage of river

### water was determined from 

### the observed total hardness of 

### the groundwater, the

### river water, and 

### the Ranney Collectorwater, assuming proportional mixing. 

### The river water percentages vary from 74.4 to 112.5%and average about 92'L. percentages exceed 100%and such anomalies can be expected, since the water analyses are spot determinations rather than average water analyses over an extended period of time. Nonetheless, it issignificant tonote that virtually all of the Ranney Collector 

### sites show 

### that in excess of 90%of the water pumped is diverted from the river, 

### thus confirming the theoretical equations of 

### Theis (1941). The 

### water produced by Ranney Collectors has a seasonal temperature variation similar to that of the surface source, except that it

### is substantially less inmagnitude. A 

### time lag will also

### exist between the surface water temperature and that of the water pumped. Thewater temperature characteristics ata number of existing Ranney Collector sites are shown inTable 3. These data show that, foraquifers deeper than 13m, the seasonal temperature range of thewater produced is 20 to 30% of the temperature range of the 

### river, and time lags of 2 to 3 months occur. For the shallower aquifers (lessthan 10

### m indepth), thetemperature range ofthewater filtered is 45 to 70% of the temperature range of the 

### river and time lags are only 1 month. Because cooler water isavailable during the summer months and warmer water during thewinter months, thisdampening of theriver water temperature cycle isan obvious advantage for cooling water suppl

### ies. Total hardness was

A few of the20 Table 2. Percentage of Pumped Water Diverted from a River, Based upon Water QualityData
Total Hardness as CaCO;, (mq/L) Ranney Ranney Collector Sampling Collector 

### River

. River Water Site Date Groundwater Water Water Percentage Anacortes, Wash. Carmichael, Calif. Charleston, Ind.

CrescentCity, Calif. Gladstone, Oreg. Kalama, Wash. Marysvi 11 

### e, Wash

# . Port Angeles, Wash. Quincy, Ill.

Sacramento, Calif. Skagit County, Wash.

Sonoma County, t a l i f .

Woodland, 

### Wash. 1968 (avg.) Aug. 1959 

### Jul. 1943 Aug. 1943 Sep. 1943 

### Oct. 1943 Nov. 1943 Dec. 1943 Aug. 1958 Aug. 1959 Mar. 1975 Jan. 1978 

### Oct. 1977 1951 (avg.) 1952 (avg.) 1953 (avg.) 1954 (avg.) Aug. 1967 

### Nov. 1954 Dec. 1954 Jan. 1955 Jul. 1959 Aug. 1959 May 1959 Nov. 1960 Mar. 1961 Aug. 1963 Aug. 1966 Nov. 1970 Apr. 1972 Sep. 1968 55 62 280 28

### 0 280 280 280 280



### - 41 34 41.4 50 945 945 945 945

76 49 46 49 48 46 190 190 190 190 190 190 190 31.7 24 21 173 178 177 186 210 221

64 34.7 25 40 45 225 209 23

### 1 218

58 22 25 26 20 21 147 129 141 142 129 132 119

13.6 22 19 154 152 160 179 210 21

### 0

64 34 26 40 45 146 158 176 163 56 20 24 26 15 19 133 108 127 143 125 123 119

12 94.O 95.3 84.9 79.7 85.8 93.1 100.0 84.3 100.0 90.0 112.5 100.0 100.0 90.1 93.5 92.8 93.0 90

## .o 93.1 95.5 100.0 84.4 92.6 75.4 74.4 77

### -8 102.1 93.8 86.6 87.3 91-9

Table 3. 

### Water Temperature Characteristics of Ranney Collectors

Ranney Collector Site Water Temperature 

### ("C) Ranney Time Lag Level (m) Max. Min. Max. Min. (months) 

### River Water Col1 ector Aquifer Depth

Below 

### River Anacortes, Wash. Carmichael, Calif. Charleston, Ind. Clinton, Ind. 

### Kennewick, Wash. Louisville, Ky. Sacramento, Calif. Sacramento, Calif. Skagit

### Co., Wash. 9.5 6.6 15.2 16.5 10.7 13.7 27.4 22.0

7.9 16.7 21.1 31.1 28.3 20.0 28.3 23.3 23.3 16.7 2.8 7.2 3.3 2.8 5.0 7.7 5.6 5.6 2.8 14.7 20.0 20.0 16.7 16.7 16.7 16.7 17.8 12.2 5.8 10.0 12.8 8.9 10.0 11.7 12.2 13.3

5.6 1 1 2.5 2 1 2.5 3 3 

### 1

### 21
COSTS. Within the capacity range of large nuclear power plant makeup cooling water supplies, the costs of Ranney Collector systems, in 1978 dollars, range from $700,000 to 

### $2,200,000 per 

### m3/s developed capacity, depending upon geological conditions and site location. These costs are for the basic Ranney Collector units and do not include the cost of pumping equipment, electrical controls, and discharge piping. 50.78 to $1.54 per kilowatt. In terms of unit cost per kilowatt, these costs range from


### As a matter of comparison, the U. S. Environmental Protection Agency ('1976) gives costs for conventional makeup water shoreline intakes ranging 

### from $1,000,000 to $2,300,000 

### per 

### m3/s, adjusted to 1978dollars. In terms of 

### unitcost 

### per kilowatt, these costs range from 

### $1.10 to $4.30 per kilowatt. Kenny and Wise (1975), indiscussinga proposed Ranney Collector system for F nuclear power plant in western Washington, state that the cost of a specially designed surface intake structure could cost on the order of twice the cost of a subsurface intake system.


### ENVIRONMENTAL ADVANTAGES Ranney Collectors offer the best available technology for minimal environmental impact. Having no direct contact with the waterway, they have no effect upon the aquatic ecosystem. Furthermore, since all construction takes place onshore, 

### no disturbance or roiling 

### of the river occurs during the construction period. The chief limitation on the use of Ranney Collectors for cooling water intakes isthat of hydrogeology. Ranney Collectors can be successfully installed only in areas where there are permeable sand and gravel aquifers connected hydraulicallywith a surface source. course, limits the sites atwhich thismethod can be applied. 

### This, of

THE RANNEY SURFACE 

### WATER INTAKE RANNEY INTAKE DESCRIPTION The Ranney SurfaceWater Intake 

### is based on 

### the same design concepts as the Ranney Collector. water supply that isprovided by the intake system. the lower portion of the caisson atan appropriate, pre-selected elevation and extend to 

### the portion of the channel that has been previously selected toprovide theintake water supply. minimize adverse environmental effects during construction, these lines areusually projected from the caisson, beneath the bank of the lake or stream, and may be designed to intercept the bank or shore ata chosen elevation, ormay be extended completely beneath the stream or lake bottom and be connected by 

### a vertical riser 

### tothe intake screens. The intake screens are located directly within the body of water serving as the water supply source. type isillustrated inFigure 

### 2, with an alternate arrangement shown 

### inFigure 3.
the intake system; 

### thus it 

### is completely redundant. open.The onshore caisson, or pumping station, isgravity-fed through 

### the intake lines. 

### turn have theintake screens located intheappropriate portion of 

### the mainstream channel. proper location of the intake screens within the stream channel and the specific design of the screens 

### is determined only 

### after careful evaluation of both the hydrology and aquatic biology of the stream. A large-diameter caisson is installed onshore and serves as the pumping station for the Two or more intake 

### lines are installed from To

A system of 

### this
In most installations, each intake line and screen 

### is designed to carry 

### theentire load of In normal operation both intake lines are
These 

### in 

### The

The intake screens and critical portions of 

### the intake lines where they join the screens are usually pile-supported. 

### steel, everdur metal, or other appropriate material. parallel to the predominant direction of current flow. entrance velocities 

### (in

### most cases lower 

### than the natural velocity of the stream current), 

### there isno tendency for suspended stream debris to impede 

### the intake, and the screens are selfcleaning innormal operation.
been installed inboth large, navigable rivers, and insmaller streams where only minimal hydraulic head isavailable. The screens 

### are perforated cylinders of carbon steel, stainless The long 

### axes of 

### the screens are aligned

By maintaining extremely low screen
Backwash facilities areprovided for extraordinary conditions. Intakes of thisdesign are applicable to either small or large demand requirements and have

### 22

Fig. 

### 2. Ranney Surface Water Intake

SCREEN

\
__

# -- ...__ ~ ~ ~ PILINGS DRlV TO STABILITY Fig. 3. Typical Ranney Intake23
OPERATIONAL FEATURES Except for the onshore pumping facilities, which are gravity-supplied through the intake lines, this complete intake system has no moving parts; hence, there isvery littleto maintain except the pumps.
located atsufficient depth toavoid most floating debris. bottom

### of the stream tominimize the effect of the abrasive products associated with sedimentation, siltation (sand and pebbles bouncing along the bottom of the stream bed), and genera7 bedload migration. move intodirect contact with the surface of the screen and float tangentially intothe screen willenter the intake lines and make itsway intothe pumping station. Thus, pump maincenance isminimal, while actual intakemaintenance 

### is practically eliminated. The pumping facilities are located onshore, above maximum flood stage, and are easily The instream intake screens, which are easily replaceable should the need .ever arise, are They are sufficiently far off the Only that small portion of the suspended load of the stream that isable to

accessible for power supply or general maintenance requirements under all conditions. installinga standby power unitwithin the pumphouse, water supply can be maintained even during total general power failure. By

ENVIRONMENTAL ADVANTAGES Openings inthe intake screens may be of any size or shape that 

### is considered to be enviThe openings should be small enough that only the smallest of organisms Inletvelocities through the screen openings are designed at 15 cm/s or Atthese inletvelocities, the smallest of fish fry can actually swim into, through, and Natural stream current velocities often actually exceed the Only by swimming directly into the screen and down the intake lineto ronmentally suitable. can enter the intake. less. out ofthe screens without injury. screen inletvelocities. the pumps can fry or larvae be injured. approach isalmost 360".
have substantially no effect on bottom-dwelling organisms. Inaddition, the screens are located inor near the mid-channel area, inmost instances, away from the near-shore, shallow-water zones where aquatic lifeismost abundant, and where most of the aquatic reproduction occurs and larval forms are most prevalent. during the short interval required for construction. Good construction procedures can minimize even this short-term, adverse effect. The potential angle of safety or escape from the screen
The screens are located sufficiently far above the bottom of the stream or lake so as to

The only significant adverse environmental effect occurs

When specialized construction techniques are utilized whereby the intake lines are hydraulicallyprojected from the bottom of the caisson toeither near or beneath the stream itself, the natural banks of the stream are not disturbed during construction, or at the very worst disturbance isminimal. minimum or are eliminated entirely. Coffer dams and major stream excavation and disturbances are kept to a
Prior tothe development ofdetailed plans and subsequent construction, site evaluation 

### is necessary. This requires a comprehensive 

### soil investigation both onshore and offshore, to determine constructiondifficulties and bearingcapacities for both the caisson pumping station and the supporting piling. Inaddition, a hydrologic evaluation of the stream isnecessary. This includes making cross-sectional and longitudinal profiles of the stream inthe vicinity of the proposed construction,, and making both horizontal and vertical measurements of stream velocities inorder to adequately describe the streamflow regime inthe vicinityof the screens. preliminary planning is frequently neglected, but is important from both the environmental and operational pointofview. Consideration should be given to the aquatic environment to be sure that the screens are properly placedwith respect to creatingthe minimum impact upon the aquatic environment. In general, nearshore and shallow-water zones should be avoided, where possible, and the screens should be placedwhere the most effective currents are available tomaximize the self-cleaning effect and minimizeany prospective future requirement for backwashing. It should be determined which portions of the stream are most likely to become debris-laden or heavy with sediment duringvarying stage conditions, and this should be considered along with other factors, such as economics, navigation channels, dock areas, etc., indetermining the proper placement ofthe screens

# - This aspect of

The greatest potential danger tothe effective and efficient long-term operation of this intake isthe improper placement of the screens within the streambed. of the operational function of the system, itisvery easy tooverlook the sophistication Because of the simplicity24 required indetermining the proper location and orientation of the screens. ating both the hydrology and the aquatic environment, the system will have minimum adverse impact, low capital and operating costs, maximum dependability and security, and ease and convenience of operation. By properly evaluDEPENDABILITY The instream intake screens are designed towithstand shocks and impacts to which they may be subjected. bility or adverse effect on either commercial river traffic or the environment. The intake lines themselves are buried and/or otherwise fully supported and protected. Backwash facilities are provided in case the screens become blocked by any unusual event. 'The dual intake lines permit the use of either

### or both screens when necessary or desirable. design 

### is such that either intake line iscapable ofcarrying the full supply load without exceeding the design entrance velocities through the screens; thus the actual capacity of all units 

### is double thatwhich is considered 

### tobe 

### the rated design capacity, and in normal opera

### tion actual entrance v.elocities through the screens are only fiftypercent of the design value. Carefullydesigned soldier pilings can be employed where necessary, without visiThe

The design of the pumping station, and its great stability due to the depth and construction of the caisson-type foundation, permits full access to the pump house and to all facilities, even during maximum floods. Direct access 

### tothe interior of the shaft of the caisson makes inspection easy and permits any repair work 

### thatmight be required. All operating machinery is protected inside the unit.

TYPICAL INSTALLATIONSAND COSTS Shown in Table 4 are installation and operation data for fivetypical Ranney Surface Water Intakes, ranging incapacity from 55,000 to 650,000 m3/day and in age from four to seventeen years. small pleasure boats; 

### two are inthe Ohio River; and one is in the Mississippi River 

### just below its confluence withthe Ohio River. Two of the units are instalTed infirm to hard shale; one is installed in metamorphic, schistose rock; and two are installed inunconsolidated materials-- alluvial sediments inriver floodplains. Comments solicited from the operators of each of these units in January of 1978 are included inthe table. application and operational effectiveness aftermany years of utilization. Two of these are installed inrelatively small, shallow streams frequented by canoes and

Clearly indicated is thediversity of

Table 4. Installation and Operation 

### Data for Five Typical Ranney Surface Water Intakes
Caisson Diameter Rated 'tear Depth of Diameter of Intake Capacity Owner Installeo Water (m) (m) Line (mn) (PI /day) River Operational Comnents Detroit Steei Corp. 1961 Portsmouth, Ohio

Ariuco Rolling Mill 1962 Ashland, hy.
Westvaco 1970 Wickliffe, Ky. American Mater Works 1973 ServiceCo. Clarion, Penn. 9.1 6.1 Two 1200 490,000 Ohio EJo problems, yearly pull R paint screens, weekly air-hydraulic backflush. 5.5 Two 4.9 Two 120G 545,000 Ohio bo problen6, very satisfactory, daily hydraulic backflush. 19.3 9.1 Two I200 650,000 Kississippi
7.9 4.4 Two 400 55,000 Clarion No oroblems, very satisfactory, weeh1 y hydraulic backflush. Pennsylvania Power 8 1975 2.4 9.1 Two 1100 272.500 Susquehanna No problenis. Light Company Watsontown. Penn.

To arriveatapproximations of 1978 costs for comparative purposes, all of these units were re-estimated interms of what the current costs of the basic units would be, i.e., exclusive of pumping equipment, electrical controls, instrumentation, and mechanical piping. The cost range, in 1978dollars, would be from $158,000 to $396,000 per 

### m3/s developed capacity, with the mean being about 6190,000 per m3/s developed capacity. As might be expected, theunitprice ishighest for low-capacity intakes and goes down substantially with the larger structures. Soils, water depth, current velocities, and related factors all contribute to variations in thepriCF. Depth of the waters in

### the rivers shown vary from 2.4 

### m to over 18.3 m atthe siteof the installations indicated.25
REFERENCES Kazmann, R. G. 1947. River infiltration asa source of ground water supply. Proc. Am. SOC. Civ. Eng. 73(6):837-853.



## . 1948. The induced infiltration of riverwater towells. Trans. Am. Geophys Union 29(1):85-89.

____c___ 

# - 1972. Modern Hydrology, 2nd ed. Harper & Row, 

### New York. 365 pp. Kenny, J. H., and K. R. Wise. 1975. Underground Water Intake for Nuclear Plant Will Protect 

### the Environment. Paper presented atthe Association ofEngineering Geologists Annual Convention, South Lake Tahoe, Calif.,.Nov. 5-6, 1975. Klaer, F. H. 1953. Providing large industrial water supplies by induced infiltration. Min. Eng. London 5:620624. 

### Mikels, F. C., and F. H. Klaer. 1956. Application of ground water hydraulics to

### the develop

### ment of water suppliesby induced infiltration, pp- 232-242. of ScientificHydrology Symposium. Darcy, Dijon. Publ. 41. 

### & International Association Rorabaugh, M. I. 1952. Stream-bed percolation in the development of water supplies. International Association of ScientificHydrology, General Assembly, Bruxelles. Vol. 2, pp. 165-174.



### . 1956. Ground-water resources of

### the northeastern part of 

### the Louisville area, Kentucky. U. S. Geol. Surv. Water-Supply Pap. 1360-8. Schreiber, D. L., C. 0. 

### Becker and 3. 3. Fuguay. 1973. Appraisal of Water Intakes 

### on the Columbia River. Battelle Memorial Institute, Pacific Northwest Laboratories. 69 pp. Silitch, E. W. 1948. The place of Ranney collectors in 

### the water supply industry. 3. 

### New Hampshire Water Works Assoc., Oct. 1948. Stone, R. 1954. Infiltration galleries. Proc. Am. SOC.Civ. Eng., Vol. 80, Separa,te No. 472, Theis, C. V. 1941. The Effect of a Well 

### on the Flow of a Nearby Stream. Trans, Am. Geophys.
U. S. Environmental ProtectionAgency. Development Document for 

### Best Technology AvailAugust 1954. 12 pp.
Union. 1976. able for the Location, Design, Construction and Capacity of Cooling Water Intake Structures forMinimizing Adverse Environmental Impact. EPA 440/7-76/015-a. Washington, 0. C. Walton, R. C. 1970. Groundwater Resource Evaluation. McGraw-Hill, 

### New York. 664 pp.HYDROLOGIC ENGINEERING CONSIDERATIONS FOR RANNEY COLLECTOR WELL INTAKE SYSTEMS
Nicholas J. Beskid Division of Environmental Impact Studies Argonne NationaI Laboratory 9700 S. Cass Avenue Argonne, I IIinois 60439

Abst ract Thebasic hydrologic aspects affecting the location, design, and operation of Ranney Collector Well intake structures are presented. erations are discussed and thetypesof problems thatrequire site-specific design considerations areoutlined. The fundamental concepts of hydrology related to collector well design, such assurface water flow regime and the more complex grounciwater hydraulics, are briefly discussed. Emphasis is placed on the application of the results of fieldpumping tests totheestimation of aquifer properties, groundwater flow, and infiltration rates and theutilization of these parameters as inputto Ranney Collector Well system design. Siting and design considINTRODUCTION 

### The Ranney Collector Well 

### is a groundwater well--a hydraulic structurewhich, when properly designed and constructed, permits economic withdrawal of water from an aquifer. years, the Ranney CollectorWell intake has become increasingly popular atpower plants 

### inareas where favorable hydrologic conditionsexist. orentrainment; pose no threat tonavigation because they are emplaced horizontally 

### atdepths below 

### the streambed; and, due.to the contribution from groundwater storage, remove lesswater from streams during low flow than do conventional stream intakes. The Ranney Collector Well supplies groundwater by the process of induced infiltration. Simply, induced infiltration, or induced recharge, 

### is the process by which 

### the cone of depression (or zone of influence) formed by 

### a pumping 

### well induces water 

### toinfiltrate through the bed of

### a nearby stream or lake.
lector Well and 

### the factors that limit 

### its installation and use, we will look ata typical i 

### nstal

### 1 

### ation. In recent Such intakes incur virtually no fish impingement

In order to discuss the hydrologic parameters which govern the operation of a Ranney ColA TYPICAL 

### RANNEY COLLECTOR WELL INSTALLATION Typically, a Ranney CollectorMe11 

### islocated 

### ina highly permeable alluvial aquiferwhere 

### The collector well (Fig. 1) 

### is constructed by lowering a cylindrical concrete caisson The construction features of collectorwells installed in 

### the water table ishigh, and indirect hydraulic contactwitha surface stream or lake (recharge source). intounconsolidated deposits, sealing the bottom witha concrete plug, and jacking perforated pipes horizontally into 

### the aquifer. the United Stateswere described by Spiridonoff (1964). The caisson is a reinforced-concrete vertical shaft, 2-1/2 to 4 

### m (8to 13ft)indiameter, poured inplace. 

### The wall thickness of the caisson 

### is 45 or 60 cm -(18

### or24 in.), depending upon whether 

### the caisson 

### is shallow 

### or deep. The bottom of the caisson 

### is a reinforced-concrete slab. One ormore tiers of horizontal perforated steel pipe (laterals)are connected to valved The lateralsusually have an outside diameter of 20 cm (8in.) and a l-cmThe ports inthe caissonwall 1.3

### m from the bottom of the caisson. than 22.5" apart. thick wall ofspecial copper-alloy steel. The slots inthe pipe are 

### cut with a saw, and are 1 cm wide and 4 cm long; theperforated area equals about 20%of the total surface area. total lengths of individual laterals range from about 35 

### to85 

### rn, generally made up of 2.4-m The ports are usually no less

2728

I Fig. 1. Ranney CollectorWell Intake. From Todd (1967) (with permission).
lengths of pipe. ina wheel. The lateralsmay fan out in

### a semicircleor ina full circle like the.spokes
Under equilibrium (steady-state) conditions, the yield of a Ranney CollectorWell is dependent 

### on aquifer thickness and permeability (transmissibility), infiltration rate through 

### the bed of 

### the recharge source, water temperature, effective radius of the collector, and distance tothe control dischargeboundary. The withdrawal efficiency of any well depends on the storage and conveyance capacities of theaquifer and 

### on the hydraulic principles governing flow toward 

### a pumping well. efficiency of a Ranney Collector Well depends inaddition upon well location and the nature of the 

### stream connected tothe aquifer. The withdrawal29 AQUIFER STORAGE AND CONVEYANCE 

### An aquifer 

### is a water-saturated geologic formation that will yield water towells ata sufficient rate that the wells can serve 

### as a practical source of water. The upper zone of saturation, just below the earth's surface, iscalled thewater table. The 

### water table 

### is used primarily in the development of Ranney Collector Wells and most shallowwells. location 

### isthe area of 

### a water table that ishydraulically connected to a nearby surface stream. A favored well


### An aquifer has two major functions--storage and conveyance. Itstores water, as a reservoir, and conveys water like 

### a pipeline. areas of recharge to areas of discharge. The groundwater inthe aquifer isconstantlymoving from
The storage capacity of 

### an aquifer isdetermined by its porosity and specificyield or coefficient of storage (S). released from storage, or taken into storage, per unit of surface area of the aquifer per unit change inhead. yield. The coefficient of storage of an aquifer is the volume ofwater Generally, forwater-table aquifers, S isessentially the same as the specific
The abilityofthe aquifer to convey water 

### is determined by 

### its permeability. Permeability isthe capacity of a porous medium to 

### transmit water. by Darcy's Law, which statesthat the flow of water through 

### a porous medium 

### is proportional to the difference in hydraulic head between ends and inversely proportional to the length traversed. 

### As in

### most mathematical expressions of natural phenomena, there 

### is a constant term in the Darcy equation. The coefficient 

### orPermeability (more appropriately, hydraulic conductivity), K, is dependent on the physical characterof the geologic formation (porosity, particle size, etc.), expressed in

### units ofgallons per day per square foot (gpd/ft*). term coefficient of transmissibility (T) torepresent the water-transmitting capability of the full thickness of an aquifer (i.e., the product of permeability and aquifer thickness). missibility can be determined from aquifer pump tests. laboratory values of permeability, which usually include inaccuraciesdue to nonrepresentative sampling. sites, aquifer transmissibility 

### is one of the most important factors considered. 

### Values range from 1000 to over 1,000,000 gpd/ft of aquifer. For large-yield intake facilities for industrial uses and generating stations, T's on 

### the order oftens of thousands to over 1,000,000 gpd/ft are required. The flow of water 

### in an aquifer 

### is described

Theis, in 1935, introduced theTransThis isan improvement over using the In determinations of Ranney CollectorMe11 feasibility and yield estimates for specific

The coefficients of transmissibility and storage are particularly important because they Where these two coefficients can be define the essential hydraulic properties ofan aquifer. determined for an aquifer, significant predictions of storage arepossible, including the specific capacity of wells of different diameters, the drawdown in the aquifer atvarious distances from a pumped well, and the drawdown ina well atany time after pumping commences.
HYDRAULICS OF FLOW TOWARD A PUMPING WELL According to Darcy's 

### Law, the velocity of flow through porous media varies directly with the hydraulic gradient. With increasinghydraulic gradient the velocity increases as flow converges toward a pumpingwell, 

### resulting ina continually steeper slope toward thewell. shape of this surface resembles a cone-shaped depression and thus is known as 

### the cone of depression. All pumping wells have a cone of depression, each differing in

### size and shape depending on pump rate, aquifer characteristics, water table slope, and recharge sources within the zone of influence of 

### the well. When water 

### is pumped from 

### a well, the discharge is initially derived from aquifer storage The

immediately surrounding the well. As pumping continues, more water 

### must be derived from storage 

### at increasingly greater distances from the well. This means that the circular-shaped cone of depression must expand 

### so that water can be drawn from greater The radius of influ- ence of thewell increases as the cone continues to expand. Drawdown also increases as the cone deepends to provide theadditional head requiredtomove the distant water. The cone expands and deepens 

### ata decreasing rate with time, however, because with each unitof horizontal expansion a larger volume of stored water isavailable. condition of equilibriumexists. There is no further increase indrawdown with increase intime of pumping. others, itmay beyears. Division 1975). water-table conditions. formula forthe water-table well is distances.

When the cone has stopped expanding; a In some wells, equilibrium occurs within a few hours after pumping begins; in
Well discharge formulae forequilibrium conditionswere derived many years ago (Johnson There aretwo basic formulae--one forartesian conditions and the other for Both assume recharge atthe periphery of the cone of depression. The

P(H2-h2 ) 

# '

= 1055 log R/r '30 where Q = well yield or pumping rate (gpm), P = permeability of the water-bearing sand (gpd/ft?), H = saturated thickness of the aquifer before pumping (ft), h = depth 

### to water while pumping (ft). R = radius of the cone of depression (ft),and r = radius of the well (ft). Theis developed the non-equilibrium well formula in 1935. This formula was the first to Its derivation was a major advance take into account the effect of pumping time on well yield. in the field of groundwater hydraulics. time after pumping begins. the early stages of a pumping test rather than afterequilibrium is reached. cients can be determined from the time-drawdown measurements ofonly a single observation well. By use of the formula, drawdown can be predicted atany 

### The transmissibility and average permeability can be determined from The aquifer coeffiINDUCED INFILTRATION When a well ispumped near a stream (recharge boundary) that is hydraulically connected to an aquifer, water isfirstwithdrawn from aquifer storage 

### inthe immediate vicinity of 

### the well. The cone of depression then spreads, drawing water from within an increasing area of influence. Water levels in the vicinity of the stream are lowered, and more and more of the water which normally would have discharged into 

### the stream isdiverted toward the pumped well. Ultimately, water levels are lowered below the surface of the stream inthe immediate vicinity of the well, and 

### the aquifer 

### is recharged by 

### the induced infiltration of surface water.

stream cannot keep pace with discharge, the cone ofdepression spreads up- and downstream. continues toexpand until itintercepts sufficient area of the 

### streambed that induced infiltration balances discharge. Recharge boundaries can be analyzed by 

### the image-well theory. Consider an aquifer bounded on one side by a stream as shown in

### Figure 2a. The cone of depression cannot spread beyond 

### the stream. effective line of recharge somewhere offshore. 

### The imaginary hydraulic system of a discharging well and its image recharge well 

### inan infinite aquifer (Fig. 2b) simulate the boundary condition shown 

### inFigure 2a. 

### An imaginary recharge well has been placed directly opposite and atthe same distance from the boundary line as the real well. 

### The recharge image well operates simultaneously and atthe same rate as 

### the real well. arithmetic summation of the components of the real-well cone of depression and the image-well cone of impression. The resultant profile of the actual cone of depression 

### is steeper on the river side of the real well and flatteron the land side of the real well than itwould be if no boundary were present, 

### thus indicating induction of river water into the groundwater aquifer.
of events after pumping which cause the capture of groundwater flow to an effluent river. sequence applies only to a single cross section; upstream and downstream hydraulic effectswould be inearlier stages of development. stream. 

### The positive differential head (+Ah) forces groundwater up through the streambed. 

### As pumping begins (Fig. 3b), the water table 

### is lowered below the river surface 

### on the right 

### side of the stream; thus a negative differential head (-Ah) pushes water from the 

### river down through 

### the streambed. On the left side of the stream a positive differential head (+Ah) still pushes water into the stream. In Figure 3c itis shown that under heavy pumping the water table isTowered completely below the streambed, and infiltration proceeds atfull potential rate. Atthis point infiltration is constantsand maximum. Itwill vary only with head conditions across the area subject tohead loss, and will not increase with additional drawdown (Rahn f968). When recharge by the induced infiltration of surfacewater from the affected reach of 

### the It

In this case, the condition isestablished that there can be 

### no drawdown along an

The resultant actual cone of depression is the

The concept of induced infiltration isshown in Figure 3, which depicts the ideal sequence This Figure 

### 3 represents natural conditions for an effluent

Underflow iscaptured and induced infiltration has begun.

The amount of water induced into an aquifer depends on the rate of pumping, infiltration rate of the streambed, distance from surface source, nature of the surface source, and natural groundwatermovement. The nature of the surface stream is important because streams can be of several different types. of 

### a stretchof stream that contributes water 

### to the zone of saturation is termed influent (Fig. 4a) with respect to the groundwater. channel from thezone of saturation because thewater table ishigher, the stream is termed effluent (Fig. 4b) withrespect to groundwater. Some sections of a stream may be influent, whereas other stretches of the same streammay be effluent. fore provides thegreatest recharge capability and ispreferred over an influent reach for optimum induced infiltration. Two types, influent and effluent are the most amenable to induced infiltration. A stream On the other hand, if water seeps into the stream
An effluent reach of 

### a stream there-

### 31

Groundsurface

Zero drawdown boundary

# -i Q Recharging

Aquifer thickness shouldbe very largecomparedto resultant drawdown near realwell.

Fig. 2. Representation of Image-Well Theory Applied to a Recharge Boundary (Perennial Stream). Sectional views of 

### (a) a discharging 

### well near a perennial stream and (b) the equivalent hydraulic system in an aquifer of infinite areal extent. From Todd (1967) (with permission).32



### Fig. 3. 

### Idealized Sequence of

### Hydraulic Events Resulting in Induced Infiltration. From Rahn (1968).33

Fig. 4. Relationship of Influent and Effluent Streams toAquifer. 

### (a)An influent stream loses water 

### to an aquifer; (b) an effluent stream gains water from the aquifer because the water table 

### is above the streambed. From Johnson Division, UOP 

### Inc. (1975) (with permission).

It

### is also important that the velocity of the surface stream be sufficient to prevent 

### silt deposition from sealing the streambed. In river reaches where currents 

### are low, orwhere flood flows no longer provide periodic scouring of the bed, silting can gradually reduce infiltration.
CONSIDERATIONS IN THE DETERMINATION OF INSTALLATION SIZE The determination of the capacity of a Ranney CollectorWell intake system requires an analysis of t.he hydraulic factors involved and 

### a characterization of 

### the proposed installation site. Such a characterization includes well drawdown and collector yield, and can best be determined by field pumping tests.
RANNEY COLLECTOR WELL DRAWDOWN The flow 

### pattern around Ranney Collector Wells isextremely complex. The thickness of 

### the aquifer and 

### the length, location, and number of laterals are important factors indetermining the drawdown distribution around such wells. laidpipes of small diameter compared to aquifer thickness. Consequently, solutions for problems of flow toward collector wells can be obtained by treating the laterals as line sinks (Hantush 1964). Analytical solutions that describe the flow toward collector wells have been obtained and some of the results are presented 

### inFigure 

### 5. face of a lateral depends 

### on 

### the geometry of the collector well. In the case of a single lateral, this point occurs at

### the middle of the lateral. Computations in

### the drawdown equations show that 

### this point approaches the face of 

### the caisson 

### of the collector well as the number of the laterals 

### is increased (Fig. 5). For a well of four ormore symmetrically located laterals, thispoint can be taken along one of the laterals atthe face of the caisson. If the number of laterals in such a well is sixormore, the same approximation can be made (Hantush 1964). Collectorwells are partially penetrating horizontally

The location of the point of maximum drawdown along the

RANNEY COLLECTOR YIELD Under equilibriumconditions, collectoryield isdependent on the following: aquifer thickness and transmissibility, infiltration rate of the streambed, water temperature, effective radius of the collector, and distance 

### to the recharge boundary. by actual measurements or indirectly by field pump tests. discharge formula and an experimentally derived equivalent-well radius. The suggested value for the equivalent-well radius 

### is approximately 75:: of the average lateral length inthe collector well system (Hantush 1964). 15MGD, of which approximately 80-90;; is derived from surfacewater through induced infiltration. All can be determined directly
The yield of a collector well isgenerallyestimated by using theDupuit-Forchheimer wellYields of Ranney Collector Wells are estimated

### torange up to34

fc = rl rl= 011

4.f = l0OI2

b‘=41

___Vertical well of depth = 41

Fig. 

### 5. Distance-Drawdown Variation in 

### the Plane of Maximum Drawdown Due to the Collectors Shown 

### ina Thick Aquifer. 

### (withpermission). 

### From Hantush (1964)

FIELD PUMPINGTESTS Knowledge of 

### the physical conditions of aquifers and of theirhydraulic properties is essential inquantitative 

### studies on collector yield. Determination of numerical values of the coefficients of storage and transmissibility 

### permits evaluation of 

### an aquifer as a source of water. through it. qualitatively significant only forhydrologic purposes. be obtained from aquifer testsby which 

### the water-bearing materials 

### are tested under natural conditions. These coefficients depend on factors characteristic of the aquifer and the water flowing Although various laboratory techniques are available, the numberical values obtained are More re1iable (integrated) values can

There are no specific 

### rules that apply to all types of pumping tests. ducted under certain prevailing conditionswhich are seldom identical in any two 

### tests. of the range of the variable factors involved, there 

### is no substitute for

### the experience and 

### judgement of qualified persons toconduct these 

### tests. The analysis of data collected during a pumping test depends largely on the selection of 

### the well-flow equation applicable to 

### the flow system under investigation and on the degree to which thebasic assumptions governing 

### the applicability of the flow equation are inaccord with the geologic characteristics of the aquifer being studied. Observed drawdown variations with time and distance from the pumped well may be interpreted inseveral ways if other supporting data, such as stream stage and water temperature, are not available. Analysis of stream flow data isnecessary

### when low-flow periods may result inreduced infiltration recharge. Streams considered 

### for a large-capacity Ranney Well intake should have a flow regime such that the withdrawal rate 

### is no more than 15%of the 7-day-10-year low flow. It must be determined from low-flow duration and frequency evaluationwhether there issufficient storage available to supply therequired withdrawal through the deficient period. be established that recharge issufficient during high-flow periods to restore the water removed from storage. Otherwise theyield of 

### the collector will steadily decline.. The most important aspect of collector design isbasic understanding of the direct interaction ofsurface and subsurface conditions. Each 

### test isconBecause

Itmust also

In collector design themost difficult factor toevaluate is whether the infiltration rate measured during the pump test ischaracteristic of average stream conditions or of some extreme.

stream conditions, and the results compared before any production unitbased upon induced infiltration isdesigned. Ideally, pump tests should be repeated during different seasons representing a variety of Because this isusually impractical, the pump 

### test should be run during35



### - 

## z

* m the season when 

### the surface stream is atlowest flow. During 

### this period channel sedimentation and organic accumulation are ata maximum and infiltration 

### is usually ata 

### minimum. If 

### it

### is not possible to 

### run the 

### pump testunder known minimal conditions, 

### then the reliability of 

### the projection tominimal conditions isdependent solely upon the experience and reliability ofthe person performing the analysis. 

### The collector installed will yield only 

### inaccordance 

### with natural conditions. 

### isexpensive orotherwise particularly important. Since the pump 

### test data are of such significance, it isgenerally necessary to 

### use several observation holes, both onshore and offshore, inmaking 

### the determinations. tions, driven well 

### points are often most convenient and economical, although itmay be necessary 

### tocorrect observed drawdowns forpartial penetration. 

### The pumping well should be of sufficient 

### size to accommodate 

### the available pumping 

### equipment. During pumping itis advisable tomaintain the highest constant 

### pumping rate possible under existing conditions. tinued ata constant rate until drawdown has stabilized 

### inall observation holes. induced infiltration conditions are present, stabilitywill usually be attained 

### inless than 

### 72 hours of pumping. 

### test repeated. recharged area. and 

### time lags forhigh efficiency are short. Hence, detailed pump testing isnecessary if the anticipated construction

In shallow formaPumping should be conWhere good If stabilitycannot be attained, the pumping rate should be reduced and 

### the In determining stability, adjustments must bemade forchanges 

### in stage of the

Where induced infiltration isgood, the river efficiency of the wells 

### is high
A typical test pattern often used for obtaining the necessary data 

### is illustrated 

### in The two lines of wells, one perpendicular to the prospective recharge boundary and Figure 

### 6. one parallel to

### it,will prove the existence of induced infiltration, ifpresent, and will supply data forthe determination of formation characteristics. points are screened approximatelyone foot beneath 

### the soil-water interface to give direct information on the infiltration conditions through the streambed.Within the streambed, 

### well

A 

## V RIVER0 

### PUMPING 

### WELL 0

### OBSERVATION WELL 

### V WELL POINT NOTE:

### Spacing of

### well points is

### optional. 

### V


# 'd
m
Fig. 6. Typical Pump Test Pattern. From Bennett (1970).

Other factors that must be considered inanalyses of pump test data include those listed below: 

# - The average depth of water inthe streamwill decrease as the result of induced infiltration; this is the estimation of potential recharge. Provided the water table remains below the streambed, the least amounts of induced infiltration occur during extended dry periods when stream-flow and thetemperature of the surface water are low. the average depth of water inthe stream and the average width of the streambed for different stages of the stream during these periods. 

# - Profiles of the stream channel can be used to determine36 

# - An aquifer test usually ismade at a pumping rate that isonly a fraction of the planned capacity of a proposed well. Where the streambed 

### is narrow, the depth ofwater inthe stream small, and the infiltration rate low, the aquifer test ata low pumping rate may indicate a certain position ofthe recharge boundary which may be invalid for a higher pumping rate. Athigher pumping rates, water may be withdrawn ata rate inexcess of the ability ofthe streambed totransmit it; as a result, the water tab1.e may decline below portions ofthe streambed. pumped well as maximum infiltration occurs inthe reach of the stream inthe immediate vicinity ofthe pumped well, and the cone of depression spreads further up- and downstreani

## . 

# -

- Insuch a case the recharge boundary moves away from the

REFERENCES Bennett, T. 

### W. 1970. On the design and constructionof infiltrationgalleries. Ground Water 8(3) 16-24. Johnson Division, UOP Inc. 1975. Ground Water and Wells. Saint Paul, Minn. 440 pp. Hantush, 

### M. S. 1964. Hydraulics of Wells, pp. 281-432. 

# InVen Te Chow (ed.), Advances in Hydroscience, Vol. 1. Academic Press, New York. Rahn, P. 

### ti. 1968. The hydrogeology of an induced streambed infiltration area. Ground Water 6(3)21:32. Spiridinoff, S. V. 1964. Design and use of radial collector wells. Paper presented at the California Section Meeting, Sanitary Engineering Association, San Francisco, Calif., Sept. 26, 1963. Theis, C. V. 1935. The relation between the lowering of the piezometric surface and the rate and duration of discharge of a well using ground water storage. Trans. Am. Geophys. Union 16:519-524. (As cited inJohnson Division, UOP Inc. [1975].) Todd, D. K. 1967. Ground Water Hydrology. John Wiley & Sons, inc. New York. 336 pp-AN ENGINEERING EVALUATION

### OF POROUS-DIKE INTAKE SCREENING SYSTEMS
John C. Roberge hIden F'esearchLebcraic.r.: torcester "0Iztechnic Irs: itute 3G Ehrewsbury Street hoIden, I:'assachuseits 'jl52C

Abstract 

### As one of many concepts currently under investigation for use in screenin9 fish and larvae frompower plant intakes, the corous-dike sysier.presents unicue chat lenses to the designer and constructor. A complete understanding of the hydraulic losses


### . through such a struciure isnecessary tc properly size and locaie the intake ar:d tc ensure proper pump selection and oerformance.
In the study described in this report, an analogy iqith frictional losses ir. COPduits was employed,and empirical data on losses were determined for three sizes ef filter stone typical of the types used ir? the construc+ionof a porous-dib,e inTake system. -hese empirical data were corncared with additional information from the literature. The dependence of hydraulic losses throuah large-diameter media on stone shape and porosity were demonstrztec although no enpirical expression of this dependence was develcped. A hypothetical porous-dike intake installation was developed, demonstrating the fundamentai design considerationswhich must be made for such a structure. Finaily, a cursory economic cornparisor! of various intake screening systems derons-trated that the porous-dike intake concept was economically competitivewith all others.

INTRODUCTION The hydraulics of flow through porous media has been extensively studied indisciplines ranging from groundwater hydrology to coastal engineering. Of particular interest inthe past decade has been the use of porous gravel structures in water intake screening systems. Conteptually, porous gravel dikeswould allow a high intake flow rate through the structure 

### ata low approach velocity, while blocking the passage 

### of fish and other waterborne organisms into the intake. Knowledge of the energy 

### loss through porous gravel structures is required for their design and construction, for both pump selection and dike stability. energy losses forvarious dike materials and flow conditions are presented in thispaper and are compared withthose inavailable literature. losses to indicatewhich parameters need further clarification and standardization. tion, 

### an economic evaluation ofa typical porous-dike intake facility is projected and a compari- son of this concept with other intake screening devices ispresented. Experimental data 

### on Analysis ismade of factors governing energy In addi

### FLOW CONDITIONS THROUGH POROUS MEDIA Flow through porous media, using an analogy withflow inconduits, has been expressed as 

### a relationship between a friction factor and a Reynolds number. dimensionless number expressing theratio of inertial toviscous forces. through porous media, the Reynolds number isdefined as The Reynolds number, IR, 

### is a In analyzing flow

IR = 

### v d/v 

### , (1) where 

### v is the superficial average velocity determined from the volume flow rate per unitcross- sectional area perpendicular to the flow, d is the mean grain diameter (dS0)of the material,

3738
and >J isthe kinematic viscosity of the fluid. Fanning,' isexpressed as The dimensionless friction factor, as defined by


### (2)
where Ah isthe piezometric head difference over the flow length L, d isthe characteristic diameter of the media (ds0), g isthe gravitational acceleration, and v 

### is the average flow velocity as defined above. The design of a porous gravel structure requires the preliminary selection of a nominal gravel diameter and average approach velocity, yielding the expected Reynolds number and thus characterizingthe state of flow. A friction factor could be obtainedfrom an empirical plot of friction factor versus Reynolds number for the chosen material, and a head loss could be c3lculated according to Equation 2, for a selected dike length. Incase the effective dike length is related tothe energy loss, an iterative solution isrequired. Ifthe energy loss isexcessive, a different material, approach velocity, and/or dike length may be selected. /

Investigations todate2-' have demonstrated a dependency of 

### fon IR inthe laminar flow range, while at higher Reynolds -numbers, the value of

### f tends toward a constant asymptotic value, independent ofIR. While littleagreement of the available data can be noted, generally these investigations have demonstrated the relative importance of media grading (porosity) and gravel shape indescribing the resistance to flow. reflectingthe dependence of the friction factor on the porosity of the media as well as on the Reynolds number. stone shape. flow resistance through porous media at high Reynolds numbers. Empirical expressions have been proposed6 More recent investigations5have recognized the less clearly defined effect of No universally accepted expression currently exists which completely describes

QUARRY STONE MATERIAL PROPERTIES To supplement existing data on energy losses through porous media, and toevaluate such information for specific porous-structure materials, three quarry stone samples with nominal sizes of 8 cm, 20 cm, and 60 cm were evaluated. granite quarry blast, yielding rough and highly angular stones similar to those commonly used in small dike and filterbed construction. The samples were graded by standard screen sieve analyses, yielding the size gradations and The graded samples were taken from a typical

distributions indicated inFigure 1. Porosity, e (defined as the ratio ofthe volume of voids to the gross volume of the sample), was evaluated for each sample by randomly dumping the test stone intoa tank with a volume of 12 m3; weighing the tank and stone; fillingthe tank with water; weighing the tank, stone, and water; arithmetically determiningthe volume of water, which was equivalent to the volume of voids; and determining the ratioofthe volume ofvoids to

WEIGHT PERCENTAGE, CUMULATIVE PASSED



# 1,

2? I 40 

# , 6? 

# , 8p 

# , 1y124 0.33 0.47 a 0.67 

## ," 0.95 - -1.35 -1.91 

### + 8 cm STONE, d50 = 4.55 cm -2.69 

# 5 -3.75 

# "

I -60.35 cn Fig. 1. QuarryStone Gradation (1 

### cm = 0.3937 in.)

120.70 100 80 60 40 20 0 WE1GHT PERCENTAGE, CUMULATIVE RETAINED39
the known volume of 

### the tank. Table 

### 1. It should be noted that the porosity of such stone samples is dependent upon 

### the placement of 

### the stones aswell as on the 

### size distribution of 

### the sample material. All samples were randomly dumped and allowed to settle naturally, both 

### in

### thevolume tank during evaluation of the porosities and 

### inthe test flume, approximately duplicating the typical placement of such material 

### inthe field. which resulted in denser packing of the stones after natural settling. The physical properties of 

### the three samples are summarized in

The quarry 

### run sample contained 

### a broader distribution of stone 

### sizes,

Table 7. QuarryStone Properties Sample Nominal Diameter Mean Diameter, d5,, Standard Deviation Porosity, e 

### 8 cm 

### 8 cm 20 

### cm 20 cm Quarry

### run 60 cm 4.55 cm 12.45 cm 25.65 cm 1.32 cm 2.95 cm 14.17 cm 0.49 0.50 0.44

EXPERIMENTAL FACILITIES Tests

### were conducted 

### in

### a rectangular steel channel approximately 18

### m long, 2.4 

### m wide, and 1.8 

### m deep (Fig. 2), sized such that boundary effects

### were minimized through the 

### test sec- tion. vertical 

### pumps. Flow rates were 

### metered by an orifice

### meter in

### the supply 

### line and controlled by valves. The inflow water was discharged into one end of 

### the channel, 

### where it passed through a baffle screen flow straightener, which damped turbulence and 

### swirl and generated approximately uniform flow through 

### the channel. through a withdrawal line situated at

### the flume bottom ateach 

### end of

### the channel. flow rate and channel water depths could be controlled by valves located in the withdrawal lines. flow 

### through the porous 

### test section. piezometers located along the channel centerline at30-cm intervals. Water flow through the channel was 

### supplied from a water storage 

### sump by a network of

Water could be withdrawn from 

### the 

### test channel by gravity Withdrawal Windows were situated 

### inthe side of the channel to

### permit directobservation

### of water Head differentials and water depths were measured by

Fig. 2. Test Facility40
INSTRUMENTATION Total inflow rates were monitored by a calibrated orifice

### meter, 6 = 0.875. differential through the orificemeter was displayed by an air-water differential manometer and measured visually on a linear scale. The visual interpretation of the differential pressure display contributed to a variation and error 

### ininflow rate measurements of up to

### 27.2%. These errors reflected additional errors of up to _+2.0% 

### inthe calculation of 

### the superficial average velocity.

meter (Fig. 3). centerline and across the channel, and approximately perpendicular to 

### the flow direction. revolution of the propellerwas sensed by a photo-electric cell and digitallydisplayed by a low-frequency analog counter. either continuous, instantaneous velocities or long-term, time-averaged velocities could be measured. The pressure

Velocity profiles inthe test channel were determined with a miniature laboratory propeller The meter was positioned atfixed intervals in

### the water column, along the The The period of 

### the analog signal could be selected such that

Fig. 3. Velocity Meter

The meter and analog counter were calibrated before 

### use inthe laboratory tow tank.
The accuracy of thevelocity measurements was approximately ~4.0%. The 

### results of each calibration yielded a plot of

### pulse counts (directly proportional to revolutions) per time period versus known speed. course of the study. These meter calibrations varied by 

### less than 

### 2.0% over the

EXPERIMENTAL PROCEDURE The quarry stone samples were tested intwo basic configurations: a trapezoidal section with upstream and downstream slopes of S = 1:1.5 and a rectangular section contained ina 

### wire mesh gabion with vertical upstream and downstream faces (Fig. 4). The trapezoidal section was41

Fig. 

### 4. Test Configurations SLOPED DIKE CONFIGURATION L=AREAabcd

RECTANGULAR ION IGURATION RECTANGULAR GAB CONF

constructedby randomly dumping the test stone into the channel and hand-placing the face stone such that a 1:1.5 slopewas achieved. 

### An additional trapezoidal section of20-cm stone

### with upstream and downstream slopes of 

### 1:l was constructed and tested to 

### determine the effects of variations 

### inmaterial volume on the friction factor forvarious inflow rates and approach velocities. A 

### wire gabion 

### with 3.8-cm mesh was used tocontain 

### the rectangular section, as depicted 

### inFigure 5.

Fig. 5. Rectangular Gabion

### 42 Velocity traverses (Fig. 6) of the channel were conducted to verify that the approach flow was uniform across the flume for both unobstructed flume flow and for flow approaching a porous dike. In a typical traverse using the miniature laboratory propeller meter, flow velocities 

### were sampled 

### at30-cm increments across the flume width and below the water surface. The maxi

### mum variation of velocity with respect to the mean channel velocity was generally less than 25% for traverses 

### atthe upstream face of the rectangular dike test section and less than 5%for flow 

### inthe unobstructed channel.



## .---

GABION CONFIGURATlON Fig. 

### 6. Velocity Profiles

DIKE CONFIGURATION The water inflow rates and the upstream approach depths were selected 

### ina manner that would insure a broad range of approach velocities and Reynolds numbers for flow through each material tested. Approach velocity and Re nolds number limits ranged from approximately 1.5 to adjusting a control valve 

### inthe flume supply line at

### the beginning of each 

### series of 

### tests. Water flow rates were monitored on a conventional air-water differential manometer. Upstream approach depths were varied by adjusting 

### the flume discharge valve, yielding several different approach velocities foreach inflow rate. A period of time, typically one hour, was required for establishment of water depth equilibrium. Approach and withdrawal depths did not vary by more than 0.03 cm for the duration of any 

### single 

### test. piezometers located along the channel centerlinewere read and water depths 

### were recorded. water temperatures 

### were recorded foreach 

### test, affording the means forproper determination of kinematic viscosity and Reynolds number.

stream face, Va, and 

### the effective flow length of dike 

### test section, L. of data forthe trapezoidal test sections, an equivalent test length was calculated based on a wetted area defined by 

### the trapezoid abcd shown 

### inFigure 5. be defined interms of 

### the dike crest width, the dike height, the dike face slope, and 

### the depth of ffow atthe upstream face of 

### the dike. The equivalent

### test length 

### is reduced to the crestwidth as 

### the dike face slopebecomes steeper (S -f 0), resulting in a rectangular section equal to that of the experimental rectangular gabions. 75 cm per second and 

### 1.5 x 

### lo3

### to3.0 x 

### 10 

# i,respectively. 

### A flow rate was established by

Once equilibrium 

### was established, Sump

Friction factor calculations were based on the average approach velocity at

### the dike upTo 

### ensure compatibility The geometry of the trapezoid can

EXPERIMENTAL RESULTS AND EVALUATION HEAD LOSS RESULTS Figures 7 and 8 depict typical hydraulic gradelines produced by flow through thequarry Data on head losses through the various dike configurations and quarry stone test sections. stone sizes are presented as a plot of friction factor, f,versus Reynolds number, IR, inFig- ure 9. The gradations ofthequarry stone test samples and the flow velocity range over which the

### tests were conducted resulted inReynolds numbers that extend from the transition phase Of laminar toturbulent flow 

### into therange offully turbulent flow. fromIR for increasing values of IR isgraphically demonstrated by the asymptotic curves, which approach 

### f values of 12 for the 8- and 20-cm stone sizes, and 60 for thequarry run test stone. The greater independence of 

### f

### 43


### The relativepositions of 

### the data curves correspond tothe decrease 

### inporosity, 

### or increase 

### in size distribution, of 

### the stonesamp'les.



## -. .- . ., Fig. 7. Hydrdulic Gradeline through SlopingDike

Data from the present 

### test series arecompared topublished data inFigure 10. 

### The rubble data4

### were forrough, angular stoneswitha porosity of approximately 0.4, with diameters ranging 

### from 1 to

### 3.4 

### cm. porositywith diameters ranging from 0.18 to 1.6 

### cm. are located in 

### the lower range of 

### f values definedby these two rough, angular samples. stream gravel 

### tests2were for smooth washed gravel with a porosity of 0.38 and dS0 = 4.32 

### cm, yielding 

### a limiting value of thefriction factor of approximately 3.0. The 8-cm quarry stone 

### tests (e= 0.49) yielded a considerably higher frictionfactorthan 

### the 

### 8-cm stream gravel (e= 

### 0.38), indicating that the effect of stone shape in flow resistance 

### is considerably more important, and can even overshadow the effect of porosity. 

### These 

### tests empirically verified the dependence of fon stoneshape. 

### Itwas, therefore, evident that stone shape and porosity affect the valueof 

### the friction factor. If 

### the relative degrees of roughness of various stone samples 

### were identical, plotsof f 

### versus IR would be sensitive only toporosity. theporosities 

### were identical, 

### f versus

### 1R would be 

### sensitive only tostone shape. average stone diameter changes only the Reynolds number. 

### Therefore, if both stone roughness and porosity areconstant, a plot of 

### fversus

### IR should be a single line, irrespective of stone size. This was verified by 

### the data shown inFigure 

### 9 for

### the 8- and 20-cm stones, and probably for the three stream gravel samples] shown in Figure 10. Figure 10forthe various investigations can, therefore, be attributedto variations inporosity and stoneroughness. 

### Future investigators should take sufficientmeasurements toquantify these controllingparameters.
the 20-cm 

### test stone

### were not significantly affected by variations involume of dike material. The friction factors for the same Reynolds numbers for the three dikeconfigurations

### were in The gravel and coal data7represent rough angular material of unknown The 8- and 20-cm quarry stone

### test results The 

### 8-cm

On the otherhand, if A change in

The scatterof 

### the data presented in



### Test results forthe rectangularand sloped (S = 1:1, S = 1:1.5) dike configurationsfor44



### Fig. 8. Hydraulic Gradeline through Rectangular Dike

10 20 cm STONE, D50 = 12.45 crnm

Fig. 

### 9. Results 

### of Experiment (7 

### cm = 

### 0.3937 

### in.)

### 45 agreement with one another; therefore no distinction or considerationof test section shape was required.

I 

### I 1r2- f Fig. 10. Energy Loss for Flow through Porous Media (1 in. = 2.54 cm)

VELOCITY OBSERVATIONS Upstream velocity traverses verified that approach velocities remained uniform immediately downstream ofthe flow-straightening baffles towithin 15 cm ofthe upstream dike face. Velocitytraverses approximately 15 cm downstreamofthe back face of a rectangular test section and the sloped dike test section indicated regions ofjet-like flow. Jet formation, caused by local variations inporosity ofthe dikematerial, resulted invelocity gradients with variations of up to600%greater than the average downstream channel velocity for all stone sizes.
porous dikes. Excessive flow velocities and head drop through the 8-cm stone dike resulted in scouring ofthe downstream dike face and subsequent failure of the entire structure (Fig. 11). The 20-cm and quarry run dike structures demonstrated relativelygreater stability atthe higher velocities; no slope failurewas observed. Jetting discharge from the downstream dike face should be a consideration inthe design of

SUMMARY 

### OF LABORATORY STUDIES Experiments were conducted tomeasure energy loss through various porous dike materials that may be used infieldapplications for screening water intakes. outwith stone sizes and flow rateswhich produced higher Reynolds numbers than inprevious investigations, and demonstrated the independence ofthe friction factor from the Reynolds number inthe fullyturbulent flow range. The following conclusions may be drawn from this These experiments were carried
study.1.
2.


### 3.
4.
5. For turbulent flow, the friction factor isaffected primarilyby stone angularity and secondarily by the porosity (related tosize distribution) ofthe sample. The characteristic stone size isnot an important parameter by itself, ifthe-shape and porosity are constant, and affects only the Reynolds number. The shape of the dike isnot important, ifthe effectiveflow lengthcan be adequately described. Stabilityof the downstream dike face isan important design parameter. head drop or flow velocity can cause slumping of the dike material. Velocity distribution offlow atthe downstream face can be highly irregular due to local variations inporosity. Excessive46



### Fig. 

### 11. Slope Failure of 8-cm- (3-in.-) Stone Dike

HYPOTHETICAL POROUS-DIKE INTAKE SCREENINGSYSTEM For a full appreciation of the scope of engineeringrequired for the installation of a porous-dike intake screening system,a 

### hypothetical installation was evaluated. Typically, largemodern power stations maintain relatively high 

### cooling water demands--on the order of 

### 60

### m3/s. thus present a potentially detrimental effect to that water system either in the vicinity of the cooling water intake or at the discharge location.
water. For the purpose of

### this example, several site assumptionswere made, including those listed in Table 2. 

### is inherent in 

### this screening system. as the principal filterbed 

### materia?. Such facilitiesare therefore comnonly constructed near large sources of

### water and
Figure 12

### depicts

### a typical power plant installation situatedon 

### a semiprotected body of The assumptionthat the porous-dike system 

### is an effective biological filter 

### In addition, the 20-cm stone (dS0 = 

### 12.45 cm) was chosen

Table 2. Hypothetical Plant Site Conditions
Water depth at the intake 7m Tidal range lm Storm surge lm Significantwave height 1.5 m 

### Cooling water demand 60

### m3/s47



# _--- - *--

NTAKE STRUCTUR

17 / 

### , DIFFUSER 

### ,

Fig. 

### 12. Typical Power Plant Installation



### The foremost concern of the design engineer isthe stabilityof 

### the porous dike structure under expected tidal and surface wave effects. Structural stability can be assured by properly armoring the dikeface. Hudson specifies design guidelines for flexible coastal structures. Employing Hudson's empirical design for

### the stated parameters results ina multi-layered breakwater design which employs 

### the 20-cm filter stone as the core and base of the structure. 

### Figure 13depicts a dike section typical of that 

### which would 

### be required atthe hypothetical location. However, loss through 

### theunderlayers 

### is significant, and can be determined forvarious flow conditions from 

### the empirical data developed above. Energy 

### loss through 

### the 500-kg stone 

### is negligible. 

# i

1

OM

30M Fig. 13. Section of Typical Porous Dike48
For this example, the minimum allowable depth atthe intake port was established at5.0 m. Atmean low water, the water depth atthe intake site is 7.0 m, therefore permitting a maximum 

### loss of 2 m through the proposed dike section. for the stated conditionscan be directly determined from Equation 2. depth of 7.0 

### m on the upstream face of the dike, a maximum approach velocity of 

### 6 

### cm/s, and ai required intake flow rate of 60 m3/s, the required circumference of the dike was determined to be 150m. To minimize the volume of stonematerial required, the dike was arranged ina circle with a radius of 25 

### m. A maximum achievable approach velocity of 6 cm/s 

### Thus, with a minimum

The proposed intake installation 

### is depicted inFigure 14.

Fig. 

### 14. Layout of Proposed Porous Dike Intake Facility



### l---*O METERS c

The placing of any structure 

### inthe aquatic environment 

### is a formidable and expensive task. A porous-dike intake system, such as that proposed above, 

### would require a large source of quarry material inaddition to extensive capabilities forwaterborne placement of these materials, includine ocean-going barges, cranes, and service boats. While 

### the cost of installing such a structure 

### is highly dependent upon local labor and material 

### supplies, this proposed installation, based upon current rates 

### inthe 

### New England area, would require approximately $200,000 for 

### the purchase and delivery of filtermaterial and armor stone'andapproximately $1,000,000 for machinery and labor toconstruct 

### the porous dike structure. porous-dike intake screening system 

### is, therefore, approximately 

### $1

### -2million. Thisestimate does not include 

### the cost of pipe, 

### pumps, 

### tunnels, etc., and therefore reflects only those costs which would be required for an effective biological screening system. The total cost of the hypothetical

In those installations 

### requiring Class 1 safety-related features, additional construction costs undoubtedly would be incurred. automatically inthe 

### event that the dike failed due 

### tofouling orclogging, would be installed inthe structure and would require an additional outlay of up to $1.5 million. For instance, emergency gates, which could be opened

The porous-dike screening concept 

### is proposed as an a1ternative 

### tocurrently accepted methods of biological screening for industrial water intakes. Richardsll describes several of the screening techniques now employed, including placement of velocity caps over vertical offshore water intakes to induce horizontal approach flow to 

### the intake; flush-mounted and angled screens todissuade fish from approaching an inlet; perforated-pipe 

### inlets which eliminate the need for screens and trash bars; and a radial well intakewhich employs a porous aquifer as the49
filter. All such screening systems require extensive structural works and sizable financial outlays. For example, a typical intakewater system fora power station situatedin

### the coastal zone would include three offshore submerged intakes with velocity cap 

### structures affixed and a screenwell structure housing a series oftraveling vertical screens. 

### The projected cost of 

### the velocity caps and the screenwell would be in

### excess of 

### $4million. Somewhat 

### less elaborate and like the porous-dike concept, yet tobe proven in the field, isthe angled screen concept with a bypass flowwhich carries fish and waterborne organisms away from the intake.

. Including fish handling facilities, 

### such an installationwould cost approximately $3million. 

### The biological performance of any one of 

### the above systems 

### is not completely defined. How

### ever, cursory economic analysis of the various systems does indicate that the porous-dike screening concept iseconomically competitive. structure atthe 

### New England Power Company's Brayton Point Station will not only demonstrate 

### the biological effectiveness of the concept, but will lend significant insight intothe long-term costs of operation and maintenance. Field installation, under typically and carefully monitored conditions, of all practical screening concepts will contribute significantly 

### to an understanding of the biological, hydraulic, and economic performance of the various systems. This understanding will enable the design engineer tomake competent and justifiable decisions for the installation of any'screening device. A proposed field installation of the porous-dike

CONCLUSIONS The porous-dike intake screening system isone of many concepts currentlybeing evaluated foruse as a fish and larval exclusion system. through porous structureswere conducted inpreparation for the field evaluation for 

### the porousdike concept atthe Brayton Point Station. Preliminary hydraulic investigations of flow A hypothetical porous-dike installation was described and

1.


### 2.

3.

4.

5.
6.

7.
8. several general conclusions can be drawn from this discourse. 1. Empirical design techniques for the design of large porous structures are available and are currently being refined. The porous-dike screening concept iseconomically competitive with other exclusion sys terns. A comparison of the various screening concepts operating under carefully monitored field conditions isrequired togain a more complete understanding of their relative engineering feasibility, biological performance, and cost effectiveness. 

### 2.
3.

REFERENCES 

### Bear, J. 1972. Dynamics of Fluids in Porous Media. Inc., New York. p. 604. Bell, M. C., R. E. Nece, and R. G. Porter. 1974. A of a Permeable Dike as a Fish Barrier. Prepared for Michigan. 30 pp. Kamel, A. M. 1969. Water Wave Transmission Through Structures. U.S. Army Engineer b!aterways Experiment Mississippi. 27 pp. American Elsevier Publishing Company, Report 

### on the Laboratory Examination Consumers Power Company, Jackson,
and Reflection by Previous Coastal Station, Corps of Engineers, Vicksburg, Kondo, H., and S. Toma. 1972. Reflection and Transmission for 

### a Porous Structure, pp. 1847-1865. In Proceedings of the Thirteenth International Conference on Coastal Engineering, Vancouver, Canada, July 1972. Nece, R. E., E. M. Wilson, and D. C. Millns. 1970. Head Losses in Gravel Packs. Civ. Eng. Public Works Rev. 65(773):1466-1467. Rose, H. E. larmaterials. Proc. Inst. Mech. Eng. 153:141-148. Ward, J. C. 1964. Turbulent flow in porous media. Proc. Am. SOC. Civ. Eng. 3. Hydraul. Div. No. HY9. pp. 1-12. Richardson, J. G. 1945. Flow Through Porous Media. in V. L. Streeter (ed.), Handbook of Fluid Dynamics. McGraw-Hill, New York. p- 1614. 1945. An investigation into the laws of flow of fluids through beds of granu-50
9. Nece, R. E., and M. C. Bell. 1973. Hydraulics of a gravel core fish screen, pp- 31-39.
- InProc. 21stAnnual Hydraulics Division Specialty Conference. Engineers. American Society of Civil
10. Shore ProtectionManual, U.S. Army Coastal Engineering Research Center, Fort Belvoir, Virginia, 1973. 955 pp. 11- Richards, R. T. 1977. Fish Screening

### - The State of the Practical Art, pp.'296-303. 

## &I Hydraulics inthe Coastal Zone. 25th Annual Hydraulics Division Specialty Conference, Texas A&M University, Aolerican Society of Civil Engineers, College Station, Texas, August 1977.

### BIOLOGICAL ASPECTS OF 

### POROUS-DIKE INTAKE STRUCTURES Bradley 

### P. Schrader and Barry

### A. Ketschke New England Power Service Co. 20 Turnpike Road Westborough, Massachusetts '01581

Abstract Current knowledge is reviewed on the potential for both adult and larval exclusionwith a porous dike. It isshown that exclusion is possible, given small enough filtermaterial. Inaddition, limited observations show that some adult and larval fish wilt avoid a porous-dike intake, thereby suggestingthat dikes can also act as behavioral barriers. Informationon fouling and clogging of porous dikes is reviewed, and proposed anti-fouling techniques are discussed. Data are too limited for predictionof flow restrictionsdue tofouling; however, it isshown that fouling is not a problem when large filter material is used in the dike. To determine the feasibility of a porous-dike intake, a pilot-scale fieldexperiment is proposed. The proposed in-situ test facility, tobe installed in Mount Hope Bay, Mass., is described. Plans to assess the exclusion capability and fouling rates of several dike materials are presented. A parallet laboratory program of larval behavioral studies isdescribed. Resultsof this study are expected in 1981.



### INTRODUCTION The porous dikeisbeing considered as one possible means of larval exclusion atpower plant cooling water intakes. It' resembles a breakwater surrounding a cooling water intake. Unlikea breakwater, however, a porous dike would have a cobble or gravel core to allow relatively free passage of water while 

### presenting a physical and behavioral barrier to aquatic organisms. Figure 

### 1 

### is a conceptual 

### view of a porous-dike intake system, showing 

### a dike cross section and a conceptual layout foran onshore intake. surrounding 

### anoffshore intake isalsopossible. achieve any desired approach velocity, simply by adjusting 

### its exposed surface area. approach velocities. Intermediate filtermaterial, probably 

### inthe gravel-to-cobble size range, may be small enough toeffect larval avoidance without quickly fouling and clogging. A porous dike application completely A porous-dike intake iseasily sized to
.The porous dike concept 

### is attractive because itmay achieve larval avoidance atlow 

### Thiswould obviate

### the need 

### for larval collection and return systems.



### FILTERING AND FOULING IN POROUS DIKES: 

### CURRENT KNOWLEDGE POTENTIAL 

### FOR FISHAND LARVAL EXCLUSION Two exciusionary mechanisms are expected tooperate 

### ina porous-dike 

### intake. Physical exclusion will occur because nothing larger than the pores inthedikewill be able to pass through. through 

### the pores may choose toavoid the dike. Behavioral exclusion 

### is also likely tooccur, as'someorganisms which could fit
Several formulae are available for predicting physical exclusion of fish by 

### a porous barrier. from 

### Bel1 (undated): The following equations for screen-mesh sizing are quoted by Sonnichsen etal. (1973)



### M = 0.04 (L 

### - 1.35)F if 5 5 F 5 6.5, and 

### M = 0.03 (L

### - 0.85)F if 6.5 I F 5.8.0, 5152

SECTION OF POROUS DIKE

-.~r.. INTAKE CANAL

~ C.,

Fig. 

### 1. Porous Dike Intake Screening Structure. By permission of theAlden Research Laboratory.



### where M = maximum 

### screen mesh opening in inches, L = length of fish 

### ininches, D = fishbody depth 

### in inches, and F = 

### L/D = 

### fineness ratio. Because these equations arederived from a small data base, they should be used only as rough guides. slightly larger openings than permitted by Bell's equations may be adequate. For comparison, Sonnichsen 

### etal. also 

### present data by Kerr (1953) which suggest that
Fisher etal. (1977) found that a screen opening 2-3 m smaller than 

### the mean body 

### depth of 

### juvenile king salmon (hcorhynchus tshmJytscha)was required 

### for physical exclusion. design 

### rule could be combined 

### with available body depth-fork length relations to provide a basis forassuring physical exclusion of various speciesand age classes.

was ascertained by Nece and Bell (1973), who citeYalin and Franke (1961): 

### This

The range of pore sizes present 

### ina porous dike, for a bed of uniform-diameter spheres,
d = 0.1550 (assuming tightest possible packing), and .d = 0.414D (assuming the loosest packing), d = the maximum diameter circlewhich can be inscribed ina pore and D = the diameter of bed particles. where


### In practice, a porous dikewill incorporatea distribution of rock sizes, resulting inlower porosities than predicted above foruniform rock size. Nevertheless, by 

### using the median rock 

### size (D50) inthe above equations, one can estimate 

### the range ofpore sizes in a dike.
exclusionof larvaewould require a finefiltermaterial. larvae 25 mm long would require a maximum pore size of about 4 mm, necessitating a filtermaterial 

### witha median diameter of about 3 

### an. filter stone (DS0= 4.5 cm) could 

### be expected to physically exclude any larvae and

### juveniles larger than 7 mm body depth (approximately 35-45 mm long). Based on the above relations, a porous dike designed to operate entirelyvia physical For example, exclusion of king salmon Conversely, a dike constructed of standard 7.6-cm (3-in.)53
In addition to the physical obstruction presented by a porous dike, there 

### is a small amountSuch behavof theory and experience 

### to suggest that avoidance of a porous dikemay also occur. ioral exclusion would enhance larval and post-larval exclusion beyond the levels predicted on the basis of physical exclusion alone.
substrate (thigmotropism), and velocity gradients (rheotaxism) (Vernberg and Vernberg 1972). These behavioral responses are expected to cause some species 

### to avoid the dark, rocky interstices of a porous dike; however, this avoidance reaction is predictableonly inisolated instances Fisher et

### al. (1977) show that shad (AZosa sapidissirnu) and striped bass (.'.?:>Fsjzc sazutil~s) will avoid a screen mesh largeenough to permit passage; on the other hand, king salmon (0izcorhyi:chus tsbytscha) aggressivelyattempt penetration. 

### In any case, 

### to allowjuvenile and adult fish avoidance where itis attempted, the proposed approach velocities atthe porous dike face (7.5-15 cm/s) are lower than the swimming speeds of 

### most species (18-110 cm/s) (New England Power Company 1976). Avoidance by larval fishmay be possible atthe lowest proposed approach velocity (1.5 cm/s). 

### Barker etal. (1977)measured the 

### swimming endurance of larval American shad (-ilnsasap~dissiira) 

### ina 

### swim speed chamber. of 

### 2.4 cm/s (0.1 fps) forapproximately 1 min and against 

### a current of 6.6 cm/s (0.2 fps) for 

### 21 sec. These are average endurance values; the individual observations show considerable scatter. increases 

### itsswim speed capability. Differences of 1 or 

### 2 mm in length may have dramatic effects on swimming response. tive locomotive abilityearly 

### in

### its larval period. on a species-by-species basis the necessary approach velocity to allow larval fish to perceive and avoid 

### an intake current. Juvenile and adult fish are known 

### to orient inresponse 

### to light intensity (phototropism),

They found that 11-mm shad could maintain their position 

### in

### a current
Barker etal. also confirm thatas 

### a fish develops from 

### an egg 

### to an adult, itquickly These results strongly suggest that a fish may acquire an effecHowever, atpresent we are unable to predict

These results also point 

### out the limited endurance of larval shad. 

### The porous dike may In this way, a larval fish exposed to a porous dike will have offer a solution 

### to the limited swimming endurance of the larvae by providing 

### a matrix of exposure and sanctuary areas. many opportunities to rest between swimming episodes. expectation of larval avoidance behavior. These include casual observation of 1arval winter flounder (PseudopZeuronectesmericanus)

### inrearing 

### tanks, and the difficulty insampling larval fishwith a pump. observed in the laboratory on several occasions. Newly hatched larvae exhibitlittle, if any, swimming ability, but asyolk-sac absorption proceeds, swimming ability increases. flounder atthis stage often swim in the vertical plane. Following yolk sac absorption and the beginning of exogeneous feeding, swimning ability is quitepronounced as the animals frequently dart after food. capture many individuals even when large numbers of larvaeare present. This perhaps 

### is due to the avoidance by larvae of the velocity field induced by 

### the pump suction.

on exclusion performance. atthe Wisconsin Electric Service Company's Lakeside Plant on Lake Michigan. penetrated 

### the large void spaces of the dike; nevertheless, a recent assessment of 

### the dike suggests that 

### it"effectively limits accessibility of fish to the Lakeside intake" (Wisconsin Electric Power Company 1976).
entrainment. and 

### juvenilepink salmon (hcorkynchusgorbusehu) from 

### a rapid sand filterof 4-mm-diameter particles. Marine Research, Inc., (1975) reports partial success infiltering zooplankton with a full-scale gravel-core dike. In two separate samplings one month apart, they found 95 and 997; reductions inbivalve larvae, 74 and 100%reductions in gastropod larvae, and 67 and 901.' reductions incopepod nauplii. However, other taxa showed unexplained density increases on the downstream sideof the dike. In addition to the above-cited work 

### on larval shad, our personal observations support the
Winter flounder reared from gametes stripped from mature fish have been Larval Additionally, attempts to sample fish larvaewith a small pump often fail to
Laboratory and field experiments on porous dikes generally support the above speculations A full-scale porous dikeof large (0.2-0.5 

### m) rubble stone 

### is operating Numerous fish have

Fine sand and gravel filters have proven 

### to be'effectiveinreducing larval and zooplankton Stober 

### et al. (1974) report 700:;. success inexcluding mysids (komgsisawatzc;zcizts)

Nece and Bell (1973) report the performance of 

### an intermediate filtermaterial, 7.6-cm Using a section of gravel 30 cm (1 

### ft)long inserted into a (3-in.) gravel (D50= 4.3 cm). narrow (30-cm) laboratory flume, penetration 

### tests were done with juvenile rainbow trout (2.5- 3 cm) and juvenile chinook salmon (5-8.5 cm). After a 20-hour exposure to a 5.8-cm/s (0.2-fps) approach velocity, 60%of the exposed rainbow trout remained upstream of the filter. Since the mean body depth of the fishwas less than the calculated pore size, this result strongly suggests behavioral exclusion. A half-hour exposure to roughly the same conditions showed 922 retention of exposed fish. intake and suggests that 

### a full-scale porous dikemight achieve an acceptable exclusion rate in the field. This shorter exposure time ismore characteristic of an unconfined, open-water54
Insummary, the limiteddata on fish behavior and on rock filters suggest that a porousdike intake may achieve a useful combination ofphysical and behavioral exclusion of fish. However, there are very limiteddata on porous dike performance under fieldconditions, and no data yet on larval exclusion capabilities.
POTENTIAL FOR FOULING Inany locale, a porous dikewill present a fresh, bare substrate for settlement by the typical rocky intertidaland sub-tidal communities of the area. Colonization, growth, and ecological succession willoccur until eventually a stable community develops. The growth of this foulingcommunity will result inincreased flow resistance (head loss) through the dike, which must be accounted for inthe initial design. The analytic basis for predicting fouling levels isprovided by theories and experiments on colonization and succession inrocky intertidal and subtidal environments. These results suggest that the fouling community may begin to stabilizewithin two years 3fdike construction (Connell 1972; Brown and Moore 1977). structurewithin a dike (where lightand algaeare absent), nor have they addressed the special condition of continuous slow unidirectional flow present ina porous dike. Furthermore, it would be extremely difficultto relatea species abundance prediction to a hydraulic head loss, were such a prediction available. However, these studies have not addressed the community

Inthe absence of quantitative fouling predictions, a few speculations about the fouling process seem justified. These hypotheses, derived from basic littoral ecology combined with experience inpower plant cooling systems, are offered as a starting point foranalyzing and combatting the fouling process. Fouling 

### is likelyto be most severe on the dike face inthe photic region ofthe subtidal zone, where attached algae growth will be most dense. Inthe dike interior, flow resistancewill be caused primarily by a seasonal bryozoan (e-g., TLlhlEu~ia sp. ) or by attached bivalves, bothcommonly observed inpower plant cooling systems. Predationis not expected toexert significant control on the fouling community, nor are flow velocities through the dike expected tobe highenough toretardsettlement of fouling organisms, nor is food expected to limitgrowth. Actual experience with rock filters innature confirms that, given a large enough filter material, fouling growth can establish a stable level without causing an intolerable resistance toflow. Large rubble-stone breakwaters inFlorida and Rhode Island show complete permeability after many years ofoperation (Roberge 1978; Anderson 1977). The rubble-stone porousdike at the Lakeside generating plant, mentioned previously, has shown no increase inflow resistance in over fiftyyears of operation (Wahtola 1977). Merced River did not foul inthree years ofoperation (Menchen 1975). A porous dike of large cobble on California's

Incontrast, filters using sand orother fine media have experienced significant fouling problems. Stober etal. (1974) report serious foulingof filters, inthe absence of corrective action. Ray etal. (1976) report that the Pennsylvania Power Ccmpany has encountered similar fouling problems withan infiltrationsystem atthe Montour power plant. Based on these results, one approach to the fouling problem isto design a porous dike with large enough filter material toavoid possible flow restrictions. fouling levels are notyet accurate enough fordesign purposes; however, proposed research (described below) will improve this predictive capability.
rock filters; however, several possible techniques are under consideration: Present methods to predict
Fouling control may also be effective. No research has been done on fouling control in



# - Backwashing with ambient water

Backwashing with heated water 

# - Backwashingwith chlorinatedwater 

# - Continuous low-level chlorination of inflowingwater 

# - Mechanical rejuvenationofthe gravel core by overturning it 

# - Replacement of isolatedcore sections Each scheme has itsown disadvantages. avoid channelingall flow through one clear area. regulatory restrictions.

, expensive and complicated. The most relevant results to date on this subjec are the experiments by Stober etal. (1974), who evaluated the firstfour options inthis liston a model rapidsand filterand found that backwashing with heated water was the most effective method.
than clogging by attached growth. Chronic, low-level accumulations of debris are expected to concentrate inthe intertidal region, causing minimal head loss. Siltationcan be prevented by Any backwashing must carefully equal ze backwash flow 

### to Rejuvenationor replacement ofcore sections would be relatively Discharges of heat and ch orine entail special

Clogging of the dike by suspended debris appears to present a less serious cleaning problem55
proper sitingand engineering 

### of the dike. weed, may ormay 

### not be a problem; because approach velocities will approximately equa: ambient current velocities, natura7 flushingmay prevent serious clogging. If necessary, itwculd be possible to sequentially isolate and backflush invididual subsections of 

### the dike, if such provisions are made in 

### the dike design. Acute seasonal clogging, e.g., by jellyfisi and 

### seaA PROFOSED RESEARCH PRGGRAM TO DEVELOP AND EVALUATE THE POROUS DIKE INTAKE The feasibilityof the porous dike intake depends on two basic considerations: exclusion The two objectives of 

### a proposed three-year program to develop 

### and evaluate the porous of 

### a significant proportion of larvae and reliabifity in supplying cooling water to 

### the power plant. dike intake are: 

# - To quantify under natural conditions the effectiveness of porous dikes of various ED%-

positions inexcluding zooplankton, fish larvae, and post-larval to adult fish. 1r.herent inthis evaluation 

### is a measurement of potential organism attrition 

### inthe dike itself. 

# - To quantify the level and composition of fouling and/or clogging of the dike on 

### a seasonal

basis. 

### To achieve these objectives, a field-testing facilitywould be constructed and used 

### for sit^. experiments. A parallel set

### of laboratory experiments on larval behavior and swimming a;ility is also planned.
DESIGN OF FIELD-TEST FACILITY AND FOULING STUDIES A field-test facilitywould be installed atBrayton Point Station, a 15OO-P.lWe fossi7-fueled steam-electric power plant owned by the New England Power Company 

### (a New England Power Service Company affiliate). Narragansett Bay (see Fig. 2). dischargechannel dike (see Fig. 3). dike 

### test facility. The station is locatedon 

### Mt. Hope Bay, an estuary comprising an ami of The field 

### test facilitywould replace a section of the existing Figure 4 is

### an artist's conception of 

### the proposed porous

Fig. 2. General Location of Brayton Point Generating Station56

c1 u) WIW Y .r n

L 0YS 03 7 n aJ c1 v) V W u) 0 0 L .r

n
a

m
0, U- .r57

Fig. 4. 

### Artist's Conception of Proposed Test Facility

The interiorof 

### the test facilitywould allow flexibility inexperimental arrangements. The plans in Figure 5 show the proposed initial experimental 

### setup, which would employ 

### test chambers separatedby impermeable dividers. Two test chambers would contain rock filtersof 7.6- and 20-cm (3- and 8-in.) stone, respectively; 

### the center chamberwould act as an unfiltered control section (required forthe field tests of screening performance). Size distributions for these and one other test material are

### shown inFigure 6. Water would flow from Mount Hope Bay through each chamber and would be pumped by a 

### single pump into the existing discharge channel. Flow rates through each chamberwould be controllableby separateweirs 

### attheir downstream 

### onds, providing 

### the flexibility to test approach velocities between 1.5 and 15cm/s 

### (0.05 and 

### 3.5 fps). The rock filterswould be constructed using easily removable gabions (large wire-mesh cages filledwith rock); thiswould allow convenient exchange of filterrock, if tests on other 

### filter naterials aredesired. )f each rock-filled chamber, sampling slotswould be built into the rock fill (typically between jabions). lets required forimpoundment tests. 

### To allow sampling atintermediate 'locations along 

### the longitudinal axis Iron framework would be provided atthe upstream end of the facility tosupport

### the
Work 

### inthis phase of the studywould quantify the growth rate of foulingorganisms 

### as a 'unction of time of year, depth, species, and rock type, and would relate fouling 

### levels to flow .esistance.58

8.7



# I

8 HOIST

PORTS 

## N 

# \

EXISTINO CHANWEL BOTTOY CL77.0

4- _. I

1.900'1 TO END OF DISCHARGE

CHANNEL, \I I I f

SCALE OF FEET nl 2- 10 20

Fig. 5. Porous Dike Test Facility for Brayton Point Generating Station

Water from Mount Hope Bay would be pumped through the test chambers at0.03 

### m/s (0.1 fps) continuously fortwo years, to stimulatemaximum fouling growth. filter rock suspended incoarse net) would be hung on 

### the upstream and downstream interfaces. Eight fouling bags would be 

### set out initially ateach end; one would be removed from each end every three months, representing the total accumulated growth since startup. of the samples would include identification of theorganisms, the biomass accrual, and an estimate ofthe percentage decrease inthe interstitial void space. Fouling bags (small samples of Laboratory analysis

Head loss measurements would be taken regularly throughout the study for each filter material. be computed and correlatedwith observed biological growth. filtersection appeared to be severely clogged, itwould be removed and replaced with an alternate test material. of the fouling community. From these data, changes inthe hydraulic friction factor 

### (f)for each material would If from head loss measurements a A portion of removed material would be carefully disassembled to allow analysis59

SIEVE OPENING, INCHES

0

10

20

30 W 2 L k 40

50

60

70

80

90

100

Fig. 

### 6. Gradations of Quarry Stone (1 

### in. = 2.54 cm). By permission of the Alden Research Laboratory.

LARVAL CULTURE AND BEHAVIORAL STUDIES In preparation for larval exclusion studies under field conditions, information on the behavior and escape capabilities of larval fish relative to a porous dike structure would be gathered under laboratory conditions. Different species of larval fishwould be reared ina laboratory facility, and 

### their escape capabilities 

### inrelation to such parameters as 

### size, water speeds, and temperature would be evaluated. 

### An indoor larval culture facilitywould be established atthe Canal Electric Plant (New England Gas and ElectricAssociation, Sandwich, Mass.). holding tanks, heating systems, and food necessary forlarval culture.
from their gametes. would be given to the species for which information on larval 

### culture is available and which appear to be particularly vulnerable to entrainment; e.g., 

### winter flounder, menhaden, stickleback, tautog, cunner, anchovy, and windowpane. Larvae would be placed ina specially designed laboratory flow system through which water speeds may be accurately regulated (Barker et

### al. 1977). Test runs in

### the laboratory would measure the maximum escape velocities of the larvae and the rapiditywithwhich fatiguemay reduce escape velocities to zero. These experiments would isolate those stages of particular species for which escape capabilities are 

### so low as to preclude their successful avoidance of any screening structure. (It isrecognized that larvae reared ina hatchery facility may not, for dietary orother reasons, be 

### ashealthy and vigorous as their: counterparts inthe wild. Therefore, these laboratory swimming/behavior testswould be viewed as worst-case experiments.) Larval behavior inthe presence of rock filterswithand without sanctuary areas alsowould be observed. These observations would provide information on possible avoidance or sanctuaryseeking behavior, and would suggest possibleareas along the dikewhere larvae may congregate. The results would factor inthe design of subsequent field tests on naturally occurring or impounded larval fish. The facility would include

### pumps, Ripe specimens of selected specieswould be collected and fertilized eggs would be obtained Larval cultures would be maintained for 

### as long as possible. Priority60
FIELD EXPERIMENTS ON BIGLOGICAL SCREENING PERFORMANCE Fish Studies Known numbers ofsmall fishwould be impounded ina mesh enclosure 

### on the upstream sideof the dike, and impingement avoidance would be evaluated as a functionofvarious parameters. The enclosure would be constructedso that the impounded fish could positionthemselves directly in the lineof flow through the dike, or ina sanctuary area not exposed tothe flow-stream into the dike. Atthe end ofthe chosen exposure period, counts would be made offish remaining on the upstream exposed side ofthe dike, offish inthe sanctuary area, and ofany fishwhich have passed through the dike. (These would He retained by a mesh barrier ina chamber on the downstream side.) Pumping would be stopped briefly atthis time, and all fish insight would be removed from the impoundment. Both the upstream and downstream chambers would be observed for several hours to determine whether any livefishhad emerged from the crevices within the dike itself. of the fish remaining alive on the upstream side ofthe dike to the number offish initially impounded.
the impingement barrierwould be conducted inthe open cell. Also, fish behavior atthe face of the dikewould be studied through the use ofviewing buckets from surface positions or by SCUBA observations. The measure ofthe performance for impingement avoidance would be defined as the ratio

For comparison with a rock filter, several parallel tests using a fixedwire-mesh screen as

Key parameters which may influence fish avoidance ofa porous dike ormovement toa sanctuary area are listed inTable 1. To quantify the influenceofthese variables, thirty-six experiments would extend over the range ofconditions listed inTable 1. Fish species would be selected for testing because they are locally available and historically vulnerable to impingement on the Brayton Point traveling screens. tested by Alden Research Laboratories ina previous phase of research (Roberge etal. 1976). The proposed filtermaterials are similar tothose

Table 1. Parameters that may Influence FishAvoidance ofa Porous Dike
Parameter Fish species

Fish length Exposure density Exposure time Ambient water temperature Lighting conditions Approach velocity Rock shape Rock size Porosity Range ofConditions Winter flounder (PseudopZeuronectes amerieanus) Si1 verside (Menidia rnenidia) Three-

### spi ne 

### sti c

### kleback 

### (GasterosteusaeuZeatus) Mummichog (Fundulus heteroczitus) Windowpane (ScophthaZmusaquosus) Cunner (Tautogolabpusudspersus) Menhaden (Brevoortia tyrannus) Alewife (Alosapseudoharengtrs) Si 1 ver hake (Ideerlucciusbizinearis) Tautog (Tautoga onitis) Bluefish (PornatomussaZtatrZx) 2-15 cm 25-500 fishper enclosure 1 /2-24 hr 0-25°C Bright sun-dark .01-.1 m/s (0.05-0.5 fps) Angular 7.6- and 20-cm (3- and 8-in.) stone .5

Naturally Occurring Ichthyoplankton Entrainment avoidance by naturally occurring larvaewould be determined by comparing filtered and unfiltered (control) chambers. isexpected to provide an estimate ofthe population exposed to entrainment in. an adjacent filtered chamber. the upstream populationwould be sampled by installinga plankton net across the unfiltered The larval population entering the unfilteredchamber (This assumptionwould be confirmed atthe start of experiments.) Accordingly,61
chamber. at intermediate locationswithin the filter. Periodically, all larvae passing a certainpoint would be collected and analyzed for species and abundance data. occur simultaneously. larvaewhich pass through the filter orare collectedwithin it. 

### In each filtered chamber, plankton nets would be mounted downstream ofthe filterand Sampling atall locations xould Analysis ofthese measurements would quantify the proportions of exposed



### In those cases where larval densities at interior and downstream sampling.points were minimal, the fate of the larvaewould be determined by sampling larval densities atthe upstream interface using a vertical liftnet or other technique developed during the laboratory phase. Larval sampling atthe fieldtest facilitywould begin when the company's regular ichthyoplankton monitoring atBrayton Point indicatedthe presence of larvae insufficient numbers for a meaningful study. calendar year. sampling day, eight 

### 100-m3 samples would be taken atone-hour intervals. Typically, the periodofsuch study would be June 15-September 15 for any Sampling would be done one .day perweek during this 13-week period. On each

. . Naturally Occurring Zooplankton Entrainment avoidance by naturally cccurring zooplankton would be quantified inthe same way as for fish larvae, comparing filtered and unfiltered chambers. zooplankton which pass through the filterorare collectedwith itwould be determined. The proportions of exposed Zooplankton sampling would be done atthe same locations as the larval fish samplicg describedabove. Dctylight sampling would be done hourly during an eight-hour periodone day per week for at leastone year. Inaddition, on a monthly basis, sampling would be undertaken every hour over a 48-hour periodto evaluate the stratification ofzooplankters inthe water column and the occurrence of certain noc,turnal zooplankters.
RESEARCH SCHEDULE AND LONG-RANGE PLANS Present plans call forcompleting installationof the test facilityby February 1979. 'Immediately thereafter, the two-year program of in-situ experiments on fouling and exclusion performance would begin. During 1978, laboratory studies of larval behavior and swimming capabilitywill be performed. At the conclusion ofthis research, data will be available to determine whether the porous dike offers a realistic prospect as a larval exclusion device for power plant intakes. If the technology still looks attractive, a full-scale demonstration of a porous dike would then be required as the next step.
SUMNARY AN5 

### CONCLUSIONS A porous-dike filterwould resemble a gravel-core breakwater surrounding a power plant coolingwater intake. large to pass through it. barrier, achieving larval exclusion by avoidance.
larval exclusion from power plant cooling water intakes. porous dike internal geometry can be used as a crude design basis to achieve physical exclusion. Laboratory results and fieldobservations suggest that avoidance by both larvae and post-larvae islikely, but design methods tomaximize avoidance are notyet available. and on a porous dike ispotentiallya problem, but this problem has been avoided at several existing porous dikes and breakwaters by the use of largefiltermaterials. available to predict flow restriction due tofouling. Several anti-fouling techniques have promise, but need tobe tested. It isnot certainatthis time whether a porous dike can successfully exclude fishand The porous dikewould present a physical barrier t o a l l organisms too However, itsprincipal promise lies i n i t s potential as a behavioral
Current information suggests that the porous dike offers promise as a means of fishand Information 

### on fish dimensions and Fouling growth in

Methods are not yet

larvae while continuing to reliablysupply coolingwater to a power plant. of field experiments on a pilot-scale porous dike isproposed. exclusion capabilities and fouling rates under natural conditions. behavior will be conducted. This researchwill determine the feasibility ofthe porous-dike intake, and determine whether further development ofthis technology 

### iswarranted. sibilitytests show promise, a full-scale demonstration of the porous dikewould follow, leading to availabilityof a new technology for larval exclusion from power plant cooling water intakes. A three-year program Laboratory studies of larval Experiments would quantiVy
Ifthe fea-62
ACKNOWLEDGEMENTS The authorswish to thank George Mathiessen, Alexander Beichek, Donald Bourne, and Richard Toner of Marine Research, Inc., for theirmajor contributions in the planning of the proposed porous dike testingprogram.

REFERENCES Anderson, M. R. 1976. 

### New England Power Service Company, Westborough, Mass., personal communication. Barker, A. J., S. Partain, and 

### F. J. Germano, 

### Jr. 1977. The collecting, culturing, and 

### swimming abilityof larval american shad, .:;OSO sapiai,-simc. Boston, Mass. 23 pp. 

### New England Aquarium Report, Bell, M. C. Undated. Handbook of Design Criteria for Fish Facilities. U. S. Army Corps of Engineers, North Pacific Division. Brown, R. T., and S. F. Moore. 1977. An Analysis of Exposure Panel Data Collected atMillstone Point, Connecticut. MIT-EL 77-015, Energy Laboratory, Massachusetts Institute of Technology, Cambridge. 158pp. (Prepublicationdraft.)

Connell, J. H. 1972. Community interactions 

### on marine rocky intertidal shores. 

### Annu. Rev. Fisher, F. W., D. 6. Odenweller, and J. E. Skinner. 1977. Recent progress infish facility research forCaliforniawater diversion projects, pp. 381-403. In L. D. Jensen (ed.), Third National Workshop on Entrainment and Impingement, EcologicTiAnalysts, Inc., Melville, N. Y. Ecol. Syst. 4~169-192.



### Kerr, J. E. 1953. Studies on fishpreservation at

### the Contra Costa steam plant of the Pacific Gas and Electric Company. Calif. Dep. Fish and Game Fish Bull. 92. Marine Research, Inc. 1975. Technical Proposal - Leaky Dam Evaluation. Marine Research, Inc., Fa7mouth, Mass. Mayo, R. 

### D. 1974. Conventional fish screening methods and some promising alternatives, pp. 277-280. In Proceedings of Second Workshop 

### on Entrainment and Intake Screening, EPRI 74-049-0015, Electric Power Research Institute, Palo Alto, Calif. Menchen, R. S. 1975. Perforated pipe used to screen and trapjuvenile salmonids. Prog. Fish Cult. 37~85-89. 

### Nece, R. E., and M. C. Bell. 1973. Hydraulics of a gravel core fish screen, pp. 31-41. In Proceedings of the 21st Annual Hydraulics Division SpecialityConference, American Sozety of Civil Engineers, New York. 

### New England Power Company. 1976. Environmental Report 

### - New England Power Units No. 1 and 2. 

### New England Power Company, Westborough, Mass. 1976. A State-of-the-Art Report on Intake Technologies. EPA-600/7-76-020, Industrial Environmental Research Laboratory, Office of Energy, Minerals and Industry, 

### U. S. Environmental ProtectionAgency. 83 ppRoberge, J. C. 1977. Alden Research Laboratory, Holden, Mass., personal communication. Roberge, 

### J. C., 

### D. C. Gramer, and

### W. E. 

### Lee. Hydraulics of Flow through Porous Gravel Sonnichsen, J. C., Jr., B. W. Bentley, G. 

### F. Bailey, and R. E. Nakatani. 1973. A 

### Review of Ray, S. S., R. L. Snipes, and D. A. Tomljanovich.

1976. Structures. 119-76/M14JF. Alden Research Laboratories, Holden, Mass. 24 pp.
Thermal Power Plant Intake 

### StructureDesign and Related Environmental Considerations. HEDL-TME 73-24, Hanford Engineering Development Laboratory. Stober, 

### Q. J., C. H. Hanson, and P. B. Swierkowski. 1974. A high-capacity sand filter for thermal power plant coolingwater intakes. Part I: Model studies and fouling control techniques, pp. 317-334. Screening 92 ppIn Proceedings of the Second Workshop 

### on Entrainment and Intake EPRI 74-049-00-5, ElectricPower Research Institute, Palo A1

### to, Calif.63


### U. S. Environmental ProtectionAgency. 1976. 

### Development Document for Best Technology Available for the Location, Design, Construction and Capacity of 

### Cooling Water Intake Structures for Minimizing Adverse Environmental Impact. EPA 440/1-76/015-a, Washington, D. 

### C. Vernberg,W. B., and F. J. 

### Vernberg. 1972. 

### Environmental Physiologyof Marine Animals. Springer-Verlag, New 

### York. 346ppWahtola, C. H., 

### Jr. 1977. 

### Wisconsin Electric Power Company, Milwaukee, personal communication. Wisconsin Electric Power Company. 1976. 

### Lakeside Power Plant 

### - Final Report on 

### Intake Monitoring Studies. Wisconsin Electric Power Company,Milwaukee. 49 

### pp. Yalin, S., 

### and 

### L. Franke. 1961. 

### Experimental investigationof 

### the laws of 

### filter flow, pp. 324-331. 

## 111 Proceedingsof the Ninth Convention of

### the International Association for Hydraulic Research, Dubrovnik, Yugoslavia.ENGINEERING ASPECTS 

### OF PASSAVANT SCREENING
Kenneth R. Siddle Solids Disposal Division

Passavant Corporation P. 0. Box 2503 Birmingham, Alabama 35201 Rajendra K. Sharma Divisionof Environmental Impact Studies Argonne National Laboratory

Argonne, Illinois60439
Abstract The Passavant screen was developed in Europe almost 30 years ago. The Passavant screen 

### is a vertical traveling screen; however, the basic difference between the conventional vertical traveling screen and the Passavant screen isthat inthe conventional screen water passes through the front screen belt and then the back screen belt, whereas inthe Passavant screen thewater enters in between the two belts and passes laterally through either of the belts. the Passavant screen isdoubled as compared tothe same size conventional vertical traveling screen. Various design and operational modifications of the Passavant screen are possible toyieldoptimum design and performance chara.cteristics which make it amenable to installation at power plants for safe removal of not only fish but also smaller organisms such as fish eggs and larvae. Inthis paper, details of the screen design and operational characteristics are discussed with notes on how these features can be modified tosuit site- and organism-specific requirements. Thus, theoreticaliy, the screening surface of

DESIGN 

### AND OPERATION The Passavant screen isa series of screening baskets connected to 

### two strands of endless chain suspended on drive sprockets supported 

### atthe operating floor. screen is held 

### inposition by 

### two steel guides which eliminate 

### theneed for underwater sprockets, shafting, and bearings. 

### As thewater flows 

### through the screening baskets, debris isretained within 

### the baskets, allowing the clean water to flow 

### through the screen. The Passavant center-flow traveling screen operates according to the internal flow system, whereby 

### the water passes through the screen from the inside to the outside. Because this

### principle 

### isused, the entire submerged screening area 

### is used 

### inthe screening procedure. screening elements. These patented baskets increase the screening area approximately 

### 60%compared to the base area of the basket frames. This special basket and a shovel-type retaining plate results 

### inoptimum efficiency of 

### the

### unit. mulates on the internal screen surface 

### from dropping back into the screening 

### unit. This also causes dewatering of 

### the trash, which results 

### in

### an increased solids concentration. waste trough inside the screen. header 

### with flat spray nozzles and 

### a cleaning device for 

### the pipe and nozzles. water discharge drain must be provided 

### on the operating floor and linked to the waste trough. TO prevent the trash from matting the screen cloth, a special electric control combined with a timer system isused. shower header. The bottom portion of the

A design feature of the Passavant screen 

### isthe application of the semicircular type of
The retaining plates prevent debris that accuAll screened particles are removed by 

### a spray from the outside and 

### are collected in-the Debris 

### isremoved from the baskets by a special screen shower 

### A special spray
Thisdelays the shutdown ofthe screen rotation and the operation of the 

### The time delay is adjustable.

6566
The semicircular screening baskets are exchangeable and have special retaining shovels. The baskets are attached to traveling non-lubricated chains that have plastic rollers and are guided 

### incast iron or steel guides. Scaling of the rotating screen against the channel walls 

### is provided by oil-resistant sealing strips.
and linked 

### toa torque tube. 

### take-up device. 

### inTable 1. The lower circular guide rows are made of cast iron.

Above the operating floor the screening baskets are driven by 

### two sprockets made of steel The number of baskets necessary for given submergence of the screen are shown The whole 

### unit isdisc-spring-suspended and equipped with a chain

Table 1. Number of'Baskets Utilized 

### atVarious Submerged Depths 

### I TOTAL NUMBER OF 

## 1

1 I' I I I I I67
MODIFICATIONS IN DESIGN 

### AND OPERATION The lower portion of 

### the screen can be adjusted to various widths to accomodate given flow conditions ("pear-shaped 

### design," Fig. 

### 1). normal rotating speed 

### is 3 fpm; tests have indicated that a rate of 

### 14 fpm 

### ismore appropriate for low-speed operation and 

### 28 fpm for high-speed operation. Operating experience and testing withvarious screening materials indicates that a polyester 

### or nylon screen media, usually

### with 

## 4mm 

### or 1 mm openings, 

### is preferable for safe screening of fish larvae. The screen can be rotated atvarious speeds. 

### The

~ ~~ Fig. 1. Design of Lower Portion of Passavant Screen68
As the screen isrotated, debris and fisharewashed off as each basket makes the turn at the upper end; thewashing spray, which isdesigned for maximum coverage, washes the matter into a trough located under the torque tube and is shaped todirect flow tothe effluent channel. The trough can be designed with a splitarrangement, whereby the fish can be gently dropped in one section and the debris inan adjoining section. isused (0.5 bass) and for the second section a higher-pressure shower isused (2 to5 bass). This arrangement allows fishto exit inone channel while the debris exits separately. Inthe first section a low-pressure shower

SCREENING OF FISH EGGS AND LARVAE The screen issuitable for screening offish, fisheggs, and larvae. The following design and operational features ofthe screen are conducive to such a use: 1.
2.


### 3.
4.

5.



### 6. The mesh size ofthe screening material forthe baskets can be selected on the basis of screening requirements. The screened organisms are retained inthe retaining lipand are not exposed to airas the basket rotates end iswashed as itmakes the pass atthe upper end of the screen structure. The screened organisms are gentlywashed intoa trough from which they can be returned to the source water body as appropriate. The screen can be rotated at high speed (28 fpm) toaccommodate increased influx of organisms and/or debris and thus organisms from the screen well can be removed without much delay. The baskets are easily removed and the screening material can be replaced. This results in bettermaintenance, and various screening materials can be used during different seasons as dictated by the screening requirements. Further changes indesign and operation are possible if the screening requirements dictate such a change. Mesh of

## 4mm size has been used satisfactorily.

Currently, engineeringand biological experimentation isunderway atthe Central Power and Light facility and the Tennessee Valley Authority research laboratory toexplore further the engineeringand biological aspects of using Passavant screens for protection of ichthyoplankton. The reader isreferred to the papers of Maglienteetal. and Murray and Jinnette inthis proceedings.

### INVESTIGATIONSON THE PROTECTIONOF FISH LARVAEAT WATER INTAKESUSING FINE-MESH SCREENING 

### IMPINGEMENT-RELEASECONCEPT: LABORATORY STUDY

### OF A 

### SINGLE-ENTRANCE, DOUBLE-EXIT,VERTICAL TRAVELING SCREEN CONCEPT
SalvatoreH. Magliente Tennessee Valley Authority Energy Research 1320 Commerce Union Bank Building

Chattanooga, Tennessee 37401


### David

## A. Tomljanovichand John 

### H. Heuer Tennessee Valley Authority Divisionof Forestry, Fisheries and Wildlife Development Norris, Tennessee 37828 

### Svein Uigander and Marvin N. Smith Tennessee Vat ley Authority Divisionof Water Management P.O. Drawer E Norris, Tennessee 37828

Abstract The Tennessee Valley Authority (TVA) is investigating the concept of protecting larval fish at power plant intakes using fine-mesh screening. The larvae can be safely impinged on the screens, washed off the screens, and returned tothe source water body (impinge-release concept). Initial studies by TVA have indicated that such a concept of screening larval fish is feasible. A single-entry, double-exit vertical traveling screen was selected for the experimental test facility. Such a screen has desirable characteristics for safe handling of fish and isamenable todesign modifications ifwarranted. Testing is designed toevaluate larval fish survival using the impinge-release concept for commercially available modified and unmodified screens. The importance of various stresses critical tosurvival of larvae will be examined under laboratory conditions



### INTRODUCTION Theprotection of fish atwater intake structureshas a 

### long history 

### in the United States, In but the enactmentof recent legislation has resulted in an intensified nationwide examinationof entrainmentand impingement effectsat power plant coolingwater intakes (Ray et al. 1976). 

### thepast, efforts have been focused on ways to reduce impingement,while entrainment has been largelyneglected. In recentyears,however, the TennesseeValley Authority (TVA) has been directing research efforts toward identifying and solving problems involved in reducing impingement and entrainmentby utilizing various screen concepts. One of the concepts that TVA is 

### investigatingtoprotect larval fishatpower plant intakes uses fine-mesh screeningto safely impingertnd return the fish to the sourcewaterbody (the impinge-releaseconcept). The basic questionsof

### this conceptwere considered in the initial TVA studies on the impinge-release concept (Tomljanovich et al. 1977). 

### In the laboratory phase of the initial studies, TVA investi

### gated the retentionof fish asa functionof (I)

### size of screen opening, (2) 

### approachwater velocity, (3) 

### fish sizeand species,and (4f

### length of time the organismswere impinged against the screen. The survival percentage of the retained fish as a functionof the variables listed
6970
above also

### was investigated. The laboratory study clearly demonstrated that (1)a relationship exists between fish retention and screen opening size, (2) impingement duration is the predominant variable affecting survival and shows 

### a strong inverse relationship 

### to survival for all taxa which responded 

### tothe test conditions, and (3) 

### low current velocities through screens provide the best survival rates. A field study was performed to provide a comparison with the laboratory screening results. Several fine-mesh screen samples (0.5- 

### to7.0-mm square mesh openings) were superimposed on 

### a conventional vertical traveling screen of a TVA steam plant. Results of this initial study indicated that 

### the concept of screening larval fish is feasible. Since the initial studies indicated 

### the biological feasibility of the concept, additional studies were directed 

### atdeveloping a feasible prototype screen. To perform satisfactorily, a prototype fine-mesh screen system must 

### (1) limit 

### impingement time for larvae to several minutes or less, (2) transport the fish from the impinged position back to the source water, and 

### (3) 

### insure high post-impingement and transport survival of the larvae which are returned to the source water. The characteristics which would permit 

### a prototype screen 

### to perform satisfactorilyare 

### (1)an endless belt arrangement of screen panels, 

### (2) vertical orientation of screen such that fish and debris are lifted out of the water, 

### (3) continuous rotation, 

### (4)a lowpressure spray to assist 

### intransferring 

### fish from the screen panel to the return channel, (5) a high-pressure spray toremove any remaining debris after the fish are transferred, and 

### (6) 

### a "fish slide" fororganisms 

### toride into a 

### return channel after being spilled from the screen panel. technology to determine the screens possessing 

### the majority of desired fish handling characteristics. 

### fish. These five types are: (1)

### a conventional vertical traveling screen equipped with fish troughs and continuous rotation, (2) a single-entry, double-exit (center-flow) vertical traveling screen with semicircular-shaped screen panels, (3) low-velocity infiltration beds, (4)

### a low-velocity slotted orperforated conduit, and (5)a horizontal traveling screen. TVA chose 

### to test and modify a dual-flow, single-entry, double-exit vertical traveling screen system because 

### ithas many good fish-handling characteristics, 

### its present design can be improved with minor modifications, 

### ithas 

### a good record of reliability and performance on intake structures, and it is available on 

### the market 

### instandardized designs. In the single-entry, double-exit vertical traveling screen system (Fig. 1), the water enters the center of the screen and passes from the inside to the outside of the screening surface. The screening material and mesh size selected for a particular sitewill vary according to the 

### fish to be protected and the type and size of debris to be screened. in an endless belt, and can be rotated continuously for extended periods of time. debris are retained inside the screen; therefore, the possibility for fish and debris carryover tothe condenser is eliminated. gravity and 

### a spray wash into an overhead sluice trough. This screening system can utilizevarious shapes of screen panels. mounted into the system. Another option is a European-designed panel (Fig. 2) in vJhich semicircular screen 

### mesh baskets provide increased screening area and facilitate 

### the removal of fish. These basket panels have a vertical lipalong the bottom to retain debris and fish in the basket 

### until 

### itrotates directly over 

### the sluice trough. After preparing the above 

### list of screen characteristics, 

### we reviewed currently available We identified five types of screen systems which may provide protection for larval

Screens are arranged Fish and The accumulated fish and debris are cleaned off the screen by
Flat panels can be



### Present industry designs do not adequately handle impinged fish, and 

### no studies have been
The study will (1) estimate fish 

### surperformed to assess the potential of this screening system to reduce entrainment. We will conduct studies 

### in 1978 focusing on the cumulative stresses associated with impingement and transport of the fish from the screen 

### to the 

### return channel. vival associated witheach aspect of fish impingement on and transfer from a mode7 screen designed to safely 

### return them tothe water body, and (2) optimize survivaT of fish by modifying those screen components which adversely affect the

### organism. plished through structural and/or operating modifications--for example, modification to structural components such 

### as the debris lipor to operational features such as screen speed.) laboratory test facilitywill be 

### used toevaluate the stresses associated with those components of the prototype screen which are critical 

### to the handling of the larvae. (This optimizationwill be accomA

SCOPE OF INVESTIGATION The four areas of the screening-transfer process and the stresses most likelyto affect fish survival are (1) impingement of larval fish on the 

### test screen panel, (2) emergence of the test panel from the water, (3)movement of thepanel from the position of emergence to a position of spilling into the trough, and (4) spilling of the panel into the return trough. ing aspects of investigation are (1) survival of fish larvae as a function of length of time The correspond-71

_Jt

SCREEN

..

. ... 

## . tCIRC. WATER PUMPS

-..

# v

..

.. 

# - EMERGENCY BYPASS GATE -EMERGENCY SCREEN BYPASS GATE



# t INFLOW 'A 

## J 

# t 

# t

HORIZONTAL CROSS 

### SECTION OF INTAKE

Fig. 

### 1. Schematic of Single-entry, Double-exit Vertical Traveling Screen
impinged, (2) survival of larvae transported on the screen panel, 

### (3) 

### survival of

### the fish transferred from the screen panel tothe 

### return trough, and 

### (4) adhesion of 

### the fish 

### tothe screen material. Biological testing 

### is designed tocompare larval fish survival on an unmodified, commer- ciallyavailable screen (presumably 

### a worst case) 

### with survival on a modified screen. procedure for investigating larval fish survival 

### is sequential. Initial 

### tests are limited to impingement only. from the water to a position of spillinginto the 

### return trough, follows the initial tests. Finally, tests will include all cumulative stresses (on both the modified and the unmodified screen panel

### f


## . The The next level of stress, exposing 

### the fish to airas 

### the screen panel travels72
HIGH-PRESSURE ~&~~i?kBRlS

SPROCKET WHEEL

DEBRIS TROUGH



# - SEMICYLINDRICAL

SCREEN PANEL

Fig. 2. European Design of Single-entry, Double-exit Vertical Traveling Screen

MATERIAL AND METHODS TEST 4PPARATUS -TVA's Water Systems Development Branch 

### is responsible for the construction of the test facility. plies thewater flow and a portion of 

### a vertical traveling endless screen belt. designed 

### to simulate the important fish handling components of a commercially available 

### singleentry, double-exit vertical traveling screen 

### with 0.5-mm openings. The components of the laboratory facilityare constructed to prototype dimensions and traveling screen kinematics. Thereby, the stresses towhich larval fish are subjected can be reproduced for a wide range of postulated prototype intake desiqns. Areas of hiqh fish stresswill be identified and screen The test apparatus (Figs. 3 and 

### 4) consists primarily of a wooden flume which supThe facility is

modifications can-bemade to obtain higher degree; of fish survival. 

### A rail-hoist system isused to

### raise and lower the screen panels out 

### One to The screen panels are raised and lowered Panels This action duplicates the kinematics of prototype screen motion. be mounted on the hoist system. systemwhich 

### is powered by a variable-speed, reversible DC motor. 

### speed from about 0.02 

### m/s toabout 0.15 

### m/s. The wooden flume is 15.2 m lona and 1.2 m deeD. A constant-head box of and into 

### the flow. four screen panels can by a drivemechanism are raised atany supplies the water. Flow comes to the head box through trol. 51-cm pipe equipped with a Howell-Bunger' valve for flow conA slide gate atthe downstream end of the flume controls water depth.


### A 0.3-m section of gravel, two 0.2-m sections of hog-hair packing 

### atthe head-box outlet, The actual test section begins roughly 2.6 

### m downstream from the head box and is 1.0 

### m wide. and a gradually contracting approach section assure relatively uniform water velocity inthe 

### flume 

### test area. Nominal velocity approaching the screen panels is0.31 m/s and ismeasured with a miniature Ott-type currentmeter. Maximum flow capacity is about 0.42 

### m3/s. The screen panels currently installed (Fig. 5) were purchased from the Passavant Corporation. Each consists of a metal frame covered with woven polyester screening material having 0.5-mm square openings and 50%open area. plate atthe lower edge to help retain the screened material until thebasket is nearly inverted. For testing purposes, the panels are equipped with an axial division baffle which splits the screens into two 0.6-m sections. screen panel, thereby permitting the investigator tomore easily retrieve 

### test fish for survival studies and counting. The panels are semicylindrical, 53 cm indiameter, and 1.2 

### m wide. 

### As indicated inFigure 5, each panel isequipped with a baffle or retaining
This division makes it possible to

### use one-half the area of a-TO



# r- I5.2IT-~ 0.2m

SLIDE J PLAN SECTION GATE YEADBOX



### SPRAYHEADER

FlSH RETURNTROUGH
SCREENWELS


## f
ELEVATION 73
TRACKS TO IMPART SIMULATED PROTOTYPE MOTION TO SCREEN BASKETS

# fFig. 4, Schematic of 

### Test Apparatus (1 m = 3.2808 ft; 1 em = 0.3937 

### in.)74

Fig. 5. Sketch of Test Panel

Two types of screens areused 

### inthe tests (Fig. 6). 

### the fish aretransported through airas all thewater 

### runs out of 

### the screen basket. second, 

### the wet screen, the fish stay submerged ina pool of water approximately 5 

### cm deep. Sealingthe lower portion of the semicylindrical baskets screen openings withepoxy paint 

### In the firsttype, 

### the dry screen, 

### In the

allows retention of the pool of water at

### the bottom of the panel. essarily indicate the depth of water that would be adequate in an operational system.) (The 5-cm depth does not necTo remove impinged fish, water 

### is sprayed through the screens from behind. For thispurThis pose, the facility 

### is equipped witha header holding six spray nozzles 

### on 15-cm centers. header 

### is positioned anywhere from the water surface to the point where 

### the baskets are inverted. Using this header or a hand-held hose, the impinged fish can be washed from the panels onto a fish slideand into a fish return trough. fish that have survived 

### the impingement. rails represents the hub of the top prototype sprocket wheel for theprojected 

### endless screen belt (Fig. 4). During preliminary testing of the laboratory facilityby TVA's Fisheries and Waterf.ow1 Resources 

### Branch, the lack of temperature control was a serious deficiency inthe 

### test facility. 

### TVA's Water Systems Development Branch 

### is now assembling a cooling system for the test facility's flume water; the system will reduce the flume water temperature approximately 

### sixteen degrees Celsius in a 27-hour period, and maintain water temperature within one degree Celsius. Sufficientwater 

### is kept inthe trough to sustain the The suspended cylinder below the arch of 

### the steel

TEST VARIABLES All tests will be conducted 

### on a screen panel having square-mesh polyester screenwith 0.5-mm openings. percentage of the smallest fish larvae entrained (Tomljanovich etal. 1977). In earlier tests, This size screen opening 

### was earlier shown to be required to retain a high75

Fig. 

### 6. Detail of Screen Panels

ronment. 1. 

### 2. 

# - 3. 4. 5. 6. 

### 7. differences 

### insurvival of impinged fish inwaters with velocities between 0.15 and 0.31 

### m/s were minimal (Tomljanovich etal. 1977); therefore, an approach water velocity of 0.31 

### m/s will be used inall tests. 

### The water temperature 

### inthe flume will correspond to the water temperature-towhich the test specieswould be exposed at

### its present life stage in

### itsnatural 

### enviThe following variables areto be evaluated 

### inthis study: Impingement duration (screenexposure 

### time) 

# - 0.5, 1.0, 2.0, and 4.0 min. Screen panel shapes 

### - semicylindrical, flat, and others. Spray volume and velocity 

### - varied increments 

### from high-volume, low-velocity to low-volume, high-velocity. Species 

### - dependent on availability during the test period. Fish developmental stage

### - prolarval, postlarval, and earlyjuvenile (depending on availability during 

### the test period). Length of 

### time test panel 

### is out of water prior to spilling of fish into return trough (airexposure 

### time) 

### - 0,5, 7.0, 2.0, and 3.0 min. Screen 

### speed 

### - 0.07, 0.11, and 0.14 

### m/s.
TEST 

### PROCEDURES The procedures for investigating larval fish survival will be conducted sequentially, 

### as described inthe section Scope of Investigation. detailed atthe outset of the study, 

### we may deviate somewhat from the schedule, depending on the Although 

### a specific testing format will be76
initial results for each species. following paragraphs. mately 0.31 

### m/s (measured

### just infront of the screen). carefully removed from the transfer-temperature adjustment container and placed in a Styrofoam cooler containing testflume water. 

### This group will represent a control for mortality associated with

### the fine-mesh screening process. testing. Each replicate 

### test will consist of 25-200 fish. The approach and basic test pattern 

### is summarized 

### inthe
Velocities Established, The water velocity in the flume will be established atapproxiApproximately 25-200 fish (dependingon availability of species) will be Survival Control.

Replication. Three replicates of each 

### test will be performed throughout all phases of Impingement Only. 

### A 

### sample of fish

### will be removed from 

### the transfer container and placed 

### ina beaker. before testing. The remaining 

### live fishwill be charged directly onto a dry screen panel. via an L-shaped 

### pipe (fish injector funnel, Fig. 4). with

### the screen fora specified duration (0.5-4 

### min). Next, the test screen panel will be raised to the surface of 

### the water; thebottom portion of the screen 

### will remain 

### immersed. 

### As the upper portion of the screen panel emerges from 

### the water, 

### the impinged fish will be gently splashed into 

### the water atthebottom of the panel. into a Styrofoam cooler. be held 

### inthe containers forup to

### 24 hours toassess delayed mortality. portion of the testing 

### will provide a control for determining 

### the effectof the additional 

### stresses associated with 

### the transfer process on 

### fish survival. These test fishwill be carefully examined and any dead fish

### will be removed 

### The fish 

### will be allowed to remain 

### incontact

The impinged fish

### will 

### then be siphoned Dead fishwill be removed and counted and the remaining 

### livefish

### will The impingement-only
Impingement-Plus

### Air Exposure. In the next phase of testing the fish

### will be impinged on 

### Atthe end of the 

### the dry screen forthe same period of time as 

### inthe impingement-only tests. impingement period, the screen containing the impinged fish will be raised completely out of 

### the water and 

### the impinged fishwill be exposed 

### to the airfor 0.5-3 

### min. to simulate travel time of the prototype screen panel from the water surface to 

### the top of 

### the screen structure. Since 

### the Screen panels 

### on the prototype are designed to travel continuously atspeeds of 0.07 to 0.14 

### m/s, a three-minute 

### airexposure represents a range of total distance from water surface to the top of the screen structure of 

### 12.8 to 25.6 

### m. screen panel will be lowered 

### until the bottom portion of the curved screen panel 

### is immersed 

### in 

### the flume water. The impinged 

### fishwill be gently splashed to the water atthe bottom of 

### the panel. This procedure will permit 

### us to siphon the test fish from the panel into a Styrofoam container, 

### thus imposing 

### minimal additional 

### stress on the fish. 

### As in the previous 

### test, the dead fishwill be immediately removed and counted and the remaining 

### live fishwill be held 

### in the container 

### 24 hours for assessment of delayed mortality. subjected to stressesassociated with impingement, airexposure, and spillingof the fish from the dry screen panel into 

### the return trough. trough (Fig. 4) will terminate approximately 1

### m below 

### the spill position. The spill distance and angle of the slidewi7l approximate those dimensions 

### inthe prototype. 

### As the screen panel reaches 

### the spill position, a wash will be varied from a high-volume, low-velocity spray toa low-volume, high-velocity spray. will berecorded as dead fish. Styrofoam container.
fishwill be impinged on a 

### wet screen, air-exposed, and sluiced. panel emerges from thewater, a spray wash will be directed behind the screen to flush-thefish into the water pool of the

### wet screen. velocity spray to a low-volume, high-velocity spray. tical tothe previous 

### tests and the 

### results willbe compared to the results from the impingementairexposure-sluicing phase using thedry screen. Adhesion of Fish on a 

### Wet Screen. In these tests, the fishwill be impinged on a wet screen and transported 

### outof the water. After the screen panel emerges from the water the fishremaining inthepool of water will be siphoned into a container and counted. screen surface will be flushed into the water pool of thewet screen. varied. Immediately following the airexposure 

### time, the

Impingement Plus

### Air Exposure 

### Plus Sluicing. In 

### this phase of testing the fishwill be 

### The 

### sheet metal fish slideand shallow 

### return

The screen.panel will be checked forunremoved fish, which The remaining fish

### will be siphoned from the trough into a 

### Fish will be treated as described for earlier

### tests. Impingement 

### Plus Air Exposure Plus Sluicing 

### on a 

### Wet Screen Panel. In 

### these 

### tests, the Immediately afterthe screen The spray wash will be varied from a high-volume, lowThe fishwill be treated 

### ina manner 

### idenThose fish left

### on the Again, spray wash wil7 be Both the fish inthe water pool and the fish

### on the screenwill be counted.


### DISCUSSION The TVA larval fishtesting will progress from an evaluation of fish survival on a basic screen with few modifications (presumably 

### a worst case) to an evaluation of fish survival on a77

screen with several fishprotectionmodifications. After all phases of testing have been completed on a species offish, the survival of the fishexposed to the entire impingement and transfer process will be compared tothe survival ofthe fishexposed only to impingement. If the survival inthe former group issignificantly less than that inthe lattergroup, testing will be repeated with additional modifications until no significant differences insurvival can be detected between the processes. Therefore, the amount of testing isdependent on the results ofeach phase. result in.optimum survival and justify an early termination of testing. testing may have toproceed through several phases to arrive atoptimum survival. It ispossible that high survival on the screen with few modificationscould On the other hand,
As test data are generated, numerical analyses will be performed. Data analyses obtained on the initial test species willprovide information that will allow for the additional testing ofthose species and for modifications to the test procedures and facility.

ACKNOWLEDGEMENTS This study isbeing funded by the U. S. Environmental Protection Agency (EPA) and conducted by the Tennessee Valley Authority (TVA) as partof the Federal Interagency EnergylEnvironment Research and Development Program. publication. policies ofeither agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. The report has been prepared by TVA and EPA and approved for Approval does not signify that the contents necessarily reflect the views and

REFERENCES Passavant Corporation. 1976. Passavant Screening Equipment Bulletin 1002, Birmingham, Alabama. Ray, 5. S., R. L. Snipes, and 

### D. A. Tomljanovich. 1976. A State-of-the-Art Report on Intake Technologies. TVA-PRS-16, EPA-600/7-76-020, PB-246-874/AS- Tennessee Valley Authority, Chattanooga, Tenn.; and Environmental Protection Agency, Research Triangle, N. C.
tionof Fish Larvae atWater Intakes Using Fine-Mesh Screening. Tennessee Valley Authority, Divisionof Forestry, Fisheries, and Wildlife Development, Norris, Tennessee. Tennessee Valley Authority, DivisionofWater Management, 1977. Vertical Traveling ScreenTest Tomljanovich, D. A., J. 

### H. Heuer, and C. W. Voigtlander. 1977. Investigationson the ProtecTechnical Note B22.

Facility. Report No. 07467. Norris, Tennessee.SURVIVAL OF DOMINANT ESTUARINE ORGANISMS IMPINGED ON FINE-MESH TRAVELING SCREENS AT THE BARNEY M. DAVIS POWER STATION 

### L. S. Murray and T. S. Jinnette Central Power and Light Company Corpus Christi , Texas

Abstract One of the primary environmental impacts associated with electric generatino stations in the United States is the loss of aquatic organisms pessing through, or impinged on, various screening media at intake structures. Historically, many +raveling screens have been fitted with 3/8-inch mesh and designed primarily to screen out aquatic organisms and debris preven? cloggirg of pumps and condenser tubes (Stupkaand Sharma 1977). Presently, comparatively new screening technologies are being evaluated by the power industry in an effort to alleviate impingement losses at power plant intakes.
An impingement study was conducted at the Barney M. Davis Power Station, Corpus Christi,Texas. The study spanned twelve months, beginning in January, 1977, and ending in December, 1977. The primary purpose of this study was to accurately describe survival of marine organisms,principally dominant fishes and shrimps, impinged on Passavani fin€-mesh center-flow traveling screens. The influence of debris loading on the survive! of selected dominant soecies also was examined.

SITE DESCRIPTION AND STUDY AREA The Barney M. 

### Davis generating station 

### is situated along the shoreline of the upper Laguna Madre near Corpus Christi, Texas (Fig; 1). The station is 

### a fossil-fuel-fired, two-unit installation. Itconsists of one oil-fired unitand 

### one gas-fired 

### unitwith a total generating capacityof 650 MWe. Madre via an intake channel 1173

### m (3850 ft)long, 2.4 m 

### (8

### ft)deep, and 23.5 m (77 ft)wide. The heated water from 

### the power plant discharges into a 457-hectare (1130-acre) perched saltwater cooling pond. Bay. Itemploys a once-through cooling system 

### using water drawn from theLaguna
From 

### this pond, cooling water isdischarged into the upper Cayo del Os0
The Laguna Madre of Texas, as characterized by Hildebrand and King (7972), isa 

### narrow coastal lagoon 209 km (130 mi) long, withan average depth of 0.8 

### m (2.5 ft). The vegetation is primarily marine spermatophytes and algae, withno marshes or intertidallyemergent grasses. Although Hedgepeth (1947) describes this lagoon as 

### a hypersaline body of water, it isnoted that fluctuations in salinityoccur as short-term oscillations. ally ranges from 30 to 50 parts per thousand. The Laguna serves as an important nursery for nany comerciallyand recreationally important marine organisms. stretches the 

### entire length of the Laguna Madre and isone of 

### its most remarkable man-made features. The salinity of this system generThe Intercoastal Waterway

INTAKE OPERATIONAL PARAMETERS 

### The Davis generating station intake structure is composed of four intake bays 4 

### m (13 ft) dide. in.) centers. :enter-flow traveling screens. jcreens and thecirculating water pumps are 12.3m (40.5 ft)behind the chlorinators. Each bay has a trash rack constructed of 73-mn of (0.5-in.) steel bars 

### set on 89-m (3.5- The chlorinators are located 2.3 

### m (7.5 ft)behind thetraveling 

### The trash racks are located 7.0 

### rn (23 ft)in front ofthe Passavant fine-mesh

7980



### Fig. 1. Overall Siteand Study Area

The 

### maximum flow rate for each intake bay 

### is 8.5 x lo4gal/min, which creates an approach velocity of 0.23 

### m/s (0.75 fps) atthe outermost trash rack. tinually over a 24-hour period. The screeps are qperated conDESCRIPTION 

### OF PASSAVANT FINE-MESH CENTER-FLOW TRAVELING SCREEN 

### ThePassavant fine-mesh center-flow traveling screen 

### is a single-entry, double-exit system that uses a setof continuous chains, fitted with 53 semicircular screening baskets (Fig. 2). 

### The screensmay be rotated ateither 0.25 or0.50 km/hr (14 or 28 ft/min). Each removable basket-orscreen panel has a shovel-type liptoaid 

### inthe retention of screened material.

. Using an inside-to-outside water flow, the 

### enti,resubmerged portion of screen functions as a screening surface. Additionally, 

### with 

### this type system 

### there is no debris carry-over as there 

### iswiththe conventional cross-flow designs. spraywitha wash pressureof 40-60 psi at230 gal./min. material into an internal spray wash trough that 

### is linked to

### the peripheral fish-handling devices. Impinged organisms are removed by an overhead Thisoutside spray washes thescreened

The mesh size of thescreen in

### use during the course of the study was 0.5 mm. The veloc

### ities through the screen were 0.5 

### m/s 

### (7.7 fps) at 100%efficiencyand 0.9 

### m/s (3.7 fps) 

### at50% efficiency


## . SAMPLE METHODOLOGY Samples were taken over a diel period 

### on a monthly basis extending from January, 1977, to December, 1977. months, sampling frequency 

### was once every sixhours for the 24-hour sample period. In January, 

### six samples 

### (one every four hours) were taken. For all other Samples were taken directly from the screen wash ateach of the four traveling screens. The samples consisted of four individual 30-second replicates taken ateach screen fora total sample time of eightminutes. Samples were collected witha 1/8-inch square mesh dip net that filtered the entirevoTume of screen wash water. placed inStyrofoam ice chests containing ambient water. The replicate samples for each screen were Debris consisting primarily of marine81

Fig. 

### 2. Passavant Center-flow Traveling Screen

spermatophytes, algae, ctenophores, and scyphozoans was removed by hand and retained for

### wet weight analysis. live and dead components. behavior was considered dead. 

### returned to

### the laboratory forweighing, measuring, enumeration, and identification of species. The remaining organisms were observed for 10-15 

### minutes and then sorted into Any organism showing visible physical damage or exhibiting erratic The sorted components were placed inmarked one-liter jars and

RESULTS AND 

### DISCUSSION During 

### the 1977 impingement study, 15species of invertebrates representing 7 families, and 

### 37 species of vertebrates representing 22 families

### were collected from the Passavant screens (Table 1). organisms

### were classified as alive and 

### 1,654 were classified as dead (Table 

### 1). 

### The overall percent survival forall individuals collected during 1977was 86.0"L. Therewas a total of 12,060 individuals collected during the study; 10,406 

### of these

The dominant speciesby total 

### numbers of individuals

### were Brevoortia patronus, Anehoa mitchilli, Mieropogon unduZatus,Penaeus azteeus, and Lucmia pma(Tables 1 through 

### 3). Monthly comparisons of dominant species collected from 

### the screen wash are shown 

### in Table 2. Greatestnumbers of individuals forthese 

### species were collected from January 1977 through May 1977 (Table 2). Fewest numbers of individuals were taken from June 1977 through December 1977 (Table 2). Hildebrand and King (19771, ina similar study on thisscreening sys

### tem, report that fall abundance inAugust and September, 1976, comprised only 12.1%of 

### the total catch, with 66.7%of the total catch collected during January, February, March, and 

### April of 1977.The lowest overall percent mortalities forthe dominant species by month occurred during These menhaden averaged 21 mm (MSL) February (Table 2). Menhaden (Brevoortiapatronus) were the most abundant fish collected during February, representing 33%of the total catch (Table 2): and mortality was 5%(Table 2). The second lowest overall percent mortalities by month occurred during April (Table2). 

### These The greatest total number of individuals collected for a singlemonth was 

### alsoduring April (Table2). menhaden averaged 25 mm (MSL) and suffered only a 4%mortality (Table 2). Menhaden represented 71%of the total sample forthismonth (Table 2).

### 82
Table 1. 

### Total Number of Individuals Collected from ScreenWash During 1977 Species 

### A1i

### ve Dead Total Invertebrates Penaeidae (shrimp)

Penaeus aztecus Penaeus duoranan Penaeus setifems 

### Palaemonidae (shrimp)

Palaemonetes intermedius PaZaemonetespugio Alpheus heterochaezis Tozewna carolinensis HippoZytepleuracantha Portunus gibbesii Catlinectessapidus Callinectes simi 

### Zis Menippe mereenaria Neopanope texana Panopeus herbstii 

### Lollinginidae (squids)

LoZZiguncula brevis 

### A1pheidae (shrimp) Hippolytidae (shrimp)
Portunidae (crabs)

Xanthidae (crabs) 962 283



### 52 71

### 4

7 8 16 

### 22

1 

### 189

0 

### 4 16



### 0 19 

### Vertebrates Elopidae (tarpons)

EZops saws (LeptocephaZus Larvae) 

### Ophichthidae (snake eels)

Gphichthus gomesi 

### Clupeidae (herrings)

Brevoortia patronus HarenguZa pensacolae 

### Engraulidae (anchovies)

Anchoa hepsetus Anchoa zyozepis Anchoa rnitchilli Ariusfezis 0pshntdsbeta Urophycisfloridanus Lepophidiwn brevibarbe Hyporhqhzis uni fasciatus StrongyZura marina Cyprinodonvariegatus Lucania parva 

### Atherinidae (silversides)

Menidia beryZlinia 

### Arridae (sea catfishes) Batrachoidi

### dae (toadfishes) Gadidae (codfishes) 

### Ophidiidae (cusk 

### eelsand brotulas) Exocoetidae (

### f

### 1yingfi

### shes,ha1fbeaks) 

### Belonidae (needle fishes) Cyprinodontidae (killifishes) 4 

### 12 43 3,868 

### 3 

### 3 

### 1 1,888 

### 14 31

0 1 6 

### 15

5 561 256 

### 31 4 

### 3 

### 2 0 

### 0 0 0 

### 0 

### 3 1 

### 0 0 

### 2 0

0 

### 0 0 

### 408

0 

### 1 0 

### 853

0 0 'I 

### 0 5 

### 2 

### 1 

### 247

31 

### 993 

### 287

55 

### 716



### 7 8 16 

### 22



### 1 192



### 1 

### 4 16



### 2 19



### 4 

### 12 43 

### 4,276 3 

### 4 1 

### 2,741 14 

### 31



### 1 1 11 

### 17

6 808 

### 28783
Tab1 e 1. Continued Species A1

### ive Dead ~ Total Sygnathidae (seahorses, pipefishes)

Hippocampuszosterae Sy,mthus Zouisianae Sygnathirs scovelli Chloroscombms chrysurus Oligoplites sums Archosargusprobatocephalus Lagodon rhomboides Bardiel

### lachrysura Cynoscionaremius Cynoscionnebulosus Leiostomus xarzthurus Micropogon una'ulatus Sciaenops ocellata Mugi11idae 

### (mu1lets)

%gi1 cepklus MugiZ curema Polynemidae (threadfins)

Polydactylus octonemus Gob b i i d a e (gobies)

Gobiosoma bcsci Gobiosoma robustwn Trichiurus lepturus Etropics crcssotus Sphoeroidesparvus Carangidae (jacks and pompanos)
Sparidae (porgies)

Sciaenidae (drums)

Trichiuridae (cutlass fish) Bothidae (lefteyed flounder) Tetraodonti dae (puffers)
Totals 18 38 28 

### 0 5 18 43 33 5 1 2 0 

### 0 1 2 1 26 0 0 

### 1 26 7 1 56 210 763

2 0 0 8 10 27

0 7 1 64 220 790

2
7 183 

### 0 

### 2 7 185
2 

### 0 2 39

4 

### 0 0 39 4
1 G 1 1 

### 0 1
12 10,406 2 1,654 14 12,060

### Table 2. 

### Monthly Composition ofDominant Species Collected from Screen Wash 

### During 1977

Mean Standard h Z Catch of Length (mm] Mortality Total Sample Species Alive Dead January, 1977

Brevoorzic pczronus Anchoc ?litehiZZ-: i&a-opooci: urduictus .?encaus azteDs Luecnic ~CrVC February, 1977

Srevoortiaptronus Ar.choanitchill: ?emeids (iiTezkc iuccniapruc &<CPopGgO7 U?& ,a;US
March, 1977

Brmoorzicpatronus Anckoc nitchilli Perdeuz CZ:EC:CS Lkcznicpcrvti 

### .. i.4icroppm UECl!s.ctas
April, 1977 (3 screens only)

Brsvoort fa::ctroniLs Anchca nitchiils' ?.?icri;.oyoi:srLuIctac Perceus czzecas Lucania parvc May, 1977

Ersrtoorzic ?ctronus Anchpa nitchili- !+icrc.zo~cn Urdulc:US F'enaeus CZZ~L-~B Luccr<c ;criic 392 506

1 274 298

539 33 12 24 2 239 24 41 20 59 ia 8 4 20 15 25 24 0.14 5 67 47
27 21 31 0 19 

### ?a 5 11 4 0 2 33 1 16 76 0 2 3 0 4 5 0 11
330 124 268 100 12 0 20 27 23 23 4 0 0 0 42 27 12 1 8 0 0 0 89 0 0 2,343

240

4 100 116

0 4 4 25 4 33 0 2 4 71 30 21 48 10 0.11 5 1 a2 a6 21 3
262 790 680 38 

### a 148 328

0 0 0 29 26 36 29 0 0 0 17 46 2 28 0.32 70 20 a5

0 214

0 23 0 26 53 92 0 0 98 0 74

1 17 46 0 0 0 0
0 50 0 2 0 72 26 0 51 1 66 130 108

0 0 15 0
0 12 5 16 0 0 35 160 96

0 0 43 0 32 0 0 0 8 25 0 September, 1977 (Unit2 down; two screens only)

Brertccrls.!-otyn,:u: 0 Anckoc *~izcktII< 1 1 :.!icrc~Gp: uezaLJiUE Perseus az:icus 3 LUCCr.C ForrtJ 0
Breooortic ;zzrcns 0 hnchoc rnt~c;IiIII I02 <viern::ogon ul~d~zotus 1 Penaeus aztecx 19 L.icazia pcrvz 9
Erevoorticpatronus 0 Mici-o.zogoz ur& Latirs 0 Luccnic ,7arva 0
Srevoortia pctrcnss 1 AnckcXftchiZii 

### aa Kierojopor; urkuistus 5 Perceus cztecx 9 iuc,-r:tz :C?"m 4 1.

October, 1977 (Unit 2 down; two screens only)

November, 1977 (Unit 2 down; two screens only)

A?;chocnttchs'lii 24 Penceus czte~as 6 December, 1977 (Unit 2 down; two screens only) 0 16 0 0 94 0 0 0 0 44

3 28 200 36 0 0 0 8 0 0
0 14 0 29 154 59

0 0 12 0 0 0 0 59

1 10 5 0 0 0
0 11 0 0 0 0 0 33 0 0 0 0 53 0 9 0 32 0 77 0
0 64 0 0 0 86 0 42 0 0.19 29

1 33 77 

### ao 0 0 2 1 1985
Table 3. 'Annual Composition of Dominant Species Collected from Screen Wash During 1977
Species Alive Dead Anchoa 

### mitchiZZi 1,888 853 

### Ejrevoortiapatronus 3,868 408 

### Micropogor.unduZatus 763 27 

### Lucaniaparva 561 247 

### Fenaeus aztecus 962 31

Total 8,042 1,566 Mean Standard /: 7: of Total No. Length (mm) Mortality Total Catch

2,741 30 31 23 4,276 10 10 35

790 78 3 7 808 19 31 7 993 69 3 8


### -- 80 9,608


## __
Highest percent mortalities of impinged organisms occurred during June (Table 2). The bay anchovy, /mhos 

### nitchiZZi, represented 74%of the total sample during June, and mortalitywas 98%(Table 2). head jellyfish 

### (StomoZophus melecgris) mixed with the screen samples. lethal to fish as well as shrimp, and have a paralytic effect on most species encountered. Hildebrand and King (1977) report that during June, 1977, mortality rates of impinged organisms were probably high due tothe presence ofjellyfish. During September, the second overall highest percent mortalityfor the dominant species was recorded (Table 2). gmzhoa 

### mitchiZZi represented44?; of the total sample and suffered a 94%mortality (Table 2). Only 39 organisms were collected from the screens during this sample period and it isdoubtful that this small number bears any statistical significance.
inTable 3. during 1977: parva, 7%; and 

### f.iicropogonunduliatus, 7% (Table 3). individuals collected. The fragile forms, Anchoa 

### mitckiZZi and

### Brevoortiapatronus, represented 58%ofthe total number of impinged organisms collected during 1977. the dominant species ranged from 10 mm for

### Brevoortia pctronus to 78 mm forMicropogon 

### unduZatus (Table 3). 

### !.!icropogonurzduZatus and 

### Penaeus aztecus incurred the lowest annual percent mortality (3%)(Table 3).. knckoa 

### mi.tckiZZi andLucaniaparva suffered the highest overall mortalities for theyear (31E) (Table 3). The Atlantic menhaden, 

### Brevoortiapatronus, incurred only a 10%mortalityduring 1977 (Table 3). This high mortalitywas directly attributable to the large numbers of cabbageThese jellyfishare quite

The annual composition ofdominant species impinged on the traveling screens isillustrated The five dominant species represent the following percentages of the total catch



### Brevooi.tiapatronus, 35%;Anchoa 

### mitchilli, 232, 

### Penaeus aztecus, 8%; 

### Lucania These species compris'ed 80%of the total Mean standard lengths for

It has been suspected that the amount of debris loading on the traveling screens has some effecten the survival of impinged organisms. Figure 3 illustrates combined monthly mortality for the dominant species versus debris weight. 

### As indicated inFigure 3, when the debris weights during January, February, and March fluctuated, the percent mortality Tollowed relatively the same pattern. The low percentmortalityduring April (Fig. 3), when debris loading was at itspeak, issomewhat puzzling; however, the composition ofthe debris may have been a factor. During spring, algal forms oftendominated the debris load, displacing the generally more abundant endemic marine spermatophytes. These algal forms are more consolidated and resilient and can be pickedfrom a biological sample much more rapidly than the loosely consolidatedmarine grasses. Similarly, itisbelieved that impinged organisms,do not become as entangled

### on the screen inthis algae as they do ingrasses. 

### As stated previously, organisms collected inMay and June (Fig. 3) suffered mortalitiesdirectly associatedwith the cabbagehead jelly fish, StomoZophus

### meieagris, and the stinging nettle jellyfish, Chrysaora 

### quinquecirrha; therefore, any relationship between debris loading and mortalityduring these months issomewhat skewed. Debris weights were relatively high during July, as were percent mortalities; however, a rather uniformdecline indebris weight and percentmortalitywas noted inAugust (Fig; 3). Only 21 individuals representing the dominant species were collected from the screens during the September sampling (Table 2). low for any significant correlation to debris, again jellyfish were probably the factor influencing mortality.. Hildebrand and King (1976) report that during September sampling the mortalityfor fishcaught on the screens atthe Davis Stationwas IOOX, due tothe overwhelming number of stinging nettle jellyfish. (Fig. 3). (Fig. 3). December (Fig. 3). Although the numbers 

### of organisms collected inSeptember are too

Percent mortalityduring October was 10.w as compared to relatively highdebris weight Percent mortalitywas relatively high inNovember and increasedsomewhat inDecember Similarly, debris weights were relatively high inNovember and increasedduring86

Xi0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 

### Fig. 3. 

### Combined Monthly Mortality for the 

### Five Dominant Species, Including Debris 

### Weight. A. 

### mitchiZZi, M. 

### unduZatus,

### L. parva, 

### and P. aztems. 

### The fivedominant specieswere B. patronis,



### CONCLUSIONS During the twelve-month impingement study atCentral Power and Light Company's Barney M. 

### The overall Davis Power Station, 12,060 organisms were collected from 

### the Passavant screens. percent survival forall individuals collected during 

### 1977was 86%. Five 

### species--Brevoortia patronus,Anchoa 

### mitchiZZi, Micropogon 

### unduZatus, Pmeus 

### azteeus, 

### and Lucania

### pama--represented 80%

### of 

### the total 

### number of individuals collected during 1977. The fragile forms, Anchoa

### mitchiZZi 

### and Brevoortia patronus, 

### represented 58%

### of 

### the total 1977 impingement catch.
lected from February through May, and fewest collected from June through December. only a 3%

### mortality during 

### the study. (Anchoa

### mitchiZZi) 

### suffered the highest mortalities fortheyear (31%). Monthly catches were highly variable, with

### the greatest numbers of dominant species colThe Atlanticcroaker (Micropogon

### unduktus)

### and brown shrimp (Penaeus azteeus) 

### incurred The rainwater killifish (herniaparva) 

### and bay anchovy
Some correlation

### between debris loading and mortality was observed during 

### seven months of 

### the year. fish 

### than any other factorduring this impingement study. It

### isbelieved however, that survival was decreased more by the occurrence of

### jellyACKNOWLEDGEMENTS The 

### authors are indebted 

### to 

### Dr. Henry Hildebrand for his 

### comments concerning this study. Thanks also go toAlfred Hesse fordrawing the figures included inthis

### paper, and toJuan De 

### Los Santos and Joe Guerra forthemany hours of laboratory and field analyses performed-tomake this

### study possible.87
REFERENCES Hedgepeth, J. 

### A. 1947. The Laguna Madre of Texas. Trans. North 

### Am. Wildl. Conf. 12:364-380. Hildebrand, H. H., and 

### D. King. 1972. A Preliminary Biological Study of the Cay0 del Os0 and the Pita IslandArea of theLaguna Madre. Annual Report toCentral Power and Light Company. 333 pp. Laguna Madre. Laguna Madre. Annual Report toCentral Power and Light Company. 297 pp.
United States. Vol. 111. Estuaries and Coastal Waters. ANL/ES-56. Prepared 

### for the U.S. Energy Research and Development Administration by Argonne National Laboratory, Argonne, 

### Ill. 310 pp. 

## . 1976. A Biological Study 

### of the Cay0 del Os0 and the 

### Pita Island Area ofthe 257 pp. A Biological Study of the Cay0 del Os0 and the,Pita 

### Island 

### Area of the Annual Report 

### toCentral Power and Light Company.



## . 1977. Stupka, R. C., and R. K. Sharma. 1977. Survey of Fish Impingement atPower Plants 

### inthe

### LARVAL EXCLUSION WITH WOVEN-SLOT, FINE-MESH SCREENING William 0. 

### Cheesmanand R. Roy Cheesman Royce Equipment Company P. 0. Box 34543 Houston, Texas 77034



### Thewoven-slot fine-mesh screen can be used for screeningof fish larval forms and is 

### adaptab’le to various screening mechanisms including the conventional vertical traveling screens and the single-entry, double-exit screen. screening have been investigated in a researchprogram at Rice University. These investigations have focused on the dynamic and kinetic factors affecting survival ofscreened organisms. results of 

### these findings the reader is

### encouraged to

### contact the authors. The hydraulic and mechanical factors of 

### fine-mesh For

89

### CURRENT 

### TVA WORK 

### ON THE FLUID MECHANICS OF 

### SCREENS WITH VERY 

### SMALL OPENINGS FOR THE 

### EXCLUSION OF

LARVA€ 

### AT POWER PLANT 

### COOLING-WATER INTAKES Svein Vigander Division of Water Managemeni

Tennessee Valley Authority

Norris, Tennessee 37828 P.0, Drawer 

### E

.

Abstract The potential use of screening media with very small openings to exclude larval fish at power plant cooling-water intakes opens several areas of possible fluid mechanic problems. In this paper, ongoing research isdescribed which focuses on four specific areas: (1) the prediction of the pressure drop across a screen, given flow rate and screen properties; (2) the estimation of the pressure drop across partially plugged screens; (3)the rate of debris buildup on a site-specific stationary screen sample; and (4) methods for stationary screen cleaning and their effectiveness, Other areas are identified in which research is needed to aid in the design of intakes that will effectively exclude larvae.



### INTRODUCTION The 

### typical power plant

### cooling-water intake in

### the Tennessee Valley area isequipped with 

### vertical traveling screens covered with

### a woven 

### steel mesh with 

### 9.5-mm openings (3/8-in.-square mesh). These screens are intended 

### to protect the cooling-water circulating pumps 

### and condenser tubes from potential problems caused by debris entrained in

### the cooling water flow. aretypically rotated once per shift

### towash the accumulated debris mat off the screening medium. 

### Themedium may be protected from mechanical damage by vertical trash bars mounted 15 to 20 

### cm apartupstream from the screen. Except for occasional undesirable approach flow conditions, these standard intake screens have posed littlechallenge from the hydraulic point of view. However, larvae and small fish thatareentrapped 

### inthe 

### approach flowmay be 

### entrained and killed, and larger fish 

### may be impinged 

### on the screens for relatively long periods and may 

### consequently suffer lethal stress 

### levels. practicability of excluding larval fish using screens with

### openings 

### so small that

### most entrapped larvaewill 

### not be entrained and in

### such a manner thatmost larvae will not suffer intolerable 

### stress levels inthe

### process of being 

### excluded from the 

### intake. -Ahost of 

### new fluid mechanic problems areencountered with 

### such an exclusion system. In thispaper we discuss current work aimed atsolving 

### these problems, which are: (1) the flow rate-pressure drop relationship for screens with 

### very small openings; (2) 

### the plugging and fouling of such screens; and 

### (3) the 

### methods necessary to clean 

### the screens. In addition, this work has led to the identification of areas inwhich 

### research 

### is needed to better design intakes that involve the interface of struc

### tures, fluid

### mechanics, and fishbehavior. The screens

Therefore, developmental work 

### is currently underway to investigate 

### the feasibility and

FLOW RATE 

### AND 

### PRESSURE DROP SCREEN NOMENCLATURE 

### Screens with 

### small openings aremanufactured and areavailable in

### many configurations. The nain variables governing flow through a screen are those that define the 

### geometry of the screen: 

### Mire cross-sectional shape, weave type ormethod of assembly, mesh sizeon both sirrfacesof the screen, and wire 

### size. Based on these basic parameters, many other secondary screen properties have been 

### formulated for the

### purpose of

### correlating pressure drop and 

### forces on the screens. 9192 

### Figure 1 

### isa definition sketch for a square-mesh screen of simple weave with 

### circular wires. The following secondary screen properties are a1

### so useful :

-d 

# x Fig. 

### 1. Nomenclature Definition for Square-mesh, Simple-weave, Round-wire Screen

Wire diameter=d (mm) Opening size 

### =

## P (mm) Mesh = m (wires per

### mm) Fractional 

### open area L 

### ct(orpercent) 

### Basic Rclationrhlps

### :

Screen opening size. The 

### sizeof the hole inthe screen 

## (x)is 

### governed by the mesh (m) 

### and thewire diameter (d):

Open 

### screen area. The 

### percent 

### or fractional open projected area (a)

### of 

### the screen is

### a function of mesh, wire diameter, orhole size:

a = (l-md)2 = (mi)* = 

### (1- $!d)’ 

### The 

### lastexpression is 

### shown graphically in

### Figure 2. Values given by a screen manufacturer agree well. specify the

### open screen area. Note that only.two of 

### the three parameters m, 

### d, and k 

### are needed to completely
Screen thickness. The total thickness (9) 

### of a simple-weave screen is B=2d. (3)93

I

v \ 4: 

### 6 a E' 

# -tLz WtW I 

### P "3 

### E I W

0tW v) W -J 0 2 

### N

I

# -'

FRACTIONALOPEN SCREENAREA, 

### a Fig. 2, Computed Relationship between Screen Properties. manufacturer are represented by dots inopen circles. The values given by a screen

Area/volume ratio. The ratio (a) of screen surface area to screen volume isgiven by the expression:
a = 12 71 m2 

### xi 

### , inwhich 

### ei isthe length of a crimped wire segment. 

### xi = (d2 

### + m-2)4


## . Void fraction. The volume void fraction (E) of the screen isgiven by E=l-' m2 d 

# . Screen wire Reynolds number. The Reynolds number (R) of the screen isbased on the wire diameter; the unobstructed, upstream flow velocity (V); and the kinematic viscosity 

### (u) ofthe fluid: IR = Vd/v 

# . The Reynolds number represents the ratio between the interial and viscous fluid forces that contribute to the pressure drop across the screen. expressed as a pressure drop coefficient (K), which isdefined as: (7)

Pressure drop coefficient. The pressure or head drop across the screen (Ah) iscomnly
Ah v2 29 (8) 

### IK=-. 

### -
The above screen propertieswere computed and are listed inTables 1 and 2 for ten simpleweave screen samples that were tested.94
Table 1. Characteristicsof Tested Screen Samples of Square-mesh, Simple-weave Screens


### Mesh per 

### Diameter of Space 

### Between Open Area, 0 

### v. No. Mater i a7

### a Inchb 

### (in.) (in.) (percent ) d 

### Wires, (1 

### - Screen Lineal Wire, d
1 2 3 4 5 6 7 

### 8 9 10 

## ss ss ss P 

## ss 

## ss P 

## ss ss a 18.0 10.0 18.0 35.3 14.0 12.0 11.1 8.0 4.0 17.0 0.023 0.035 0.0173 0.0087 0.0204 0.0181 0.0197 0.0258 0.0475 0.011 0-0326 0.065 0.0383 0.0197 0.051 0.065 0.0709 0.099 0.203 0.048 ~~~~ 34.4 42.3 47.4 48.2 51-0 61.2 61.2 63.0 65.6 66.1 1.43 1.85 2.20 2.27 2.50 3.59 3.60 3.80 4.26 4.36

= Stainless steel P = Polyester a = Aluminum. bTo convert inches to millimeters, multiply by 25.4.

Table 2. Computed Screen Propertiesa for Square-mesh, Simple-weave Screens
Pressure Drop Void Opening Wire Segment Coefficient Screen Thickness, Ratio, Fraction, Size Length, for R=100, Screen Area/Vol

### ume 

### No. B (ft)b a (per 

### ft) E(-) (ftP .ti (in.)c K(-)

1 0.0038 734.5 0.648 0.00271 0.0601 5.13 2 0.0058 399.6 0.709 0.00542 0.1060 3.16 3 0.0029 710.9 0.744 0.00319 0.0582 2.35 4 0.0087 1390.5 0.748 0.00164 0.0296 2.27 

### 5 0.0034 549.0 0.767 0.00425 0.0743 1.92 6 0

# -0030 463.1 0.825 0.00544 0.0853 1.09 7 0.0033 428

# -3 0.824 0.00587 0.0922 1-11 

### 8 0.0043 307.9 0.835 0.00827 0.1276 0.99 9 0.0079 153.2 0.848 0.01690 0.2540 0.85 io 0.0018 652.0 0.851 0.00400 0.0598 0.83 Units according to Reference 8.
To convert inches tomillimeters, multiply by 25.4. 

### a bTo convert 

### feet tometers, multiply by 0.30480. C95 

### Figure 3 is 

### a definition sketch for a wedge-wire, welded screen. For this 

### type of screen the important secondary properties aredefined as follows: Open screen area. 

### An equation for the percent or fractional open area (CY) 

### of a wedge-wire screen material can be derived from the screen geometry and is:



### the symbols 

### of which are defined in

### Figure 3. 14

### are included inTable 3. 

### Computed values of CY 

### for screen 

### Nos. 11 through 

# v$lr

d

DETAIL 

### B 

# 4See

DETAIL A

See detail 8 

# 4 detoil A



### Fig. 3. 

### Nomenclature Definition for Welded, Wedge-wire Screen

Table 3. 

### Characteristics 

### of Tested Screen Samples 

### of Welded, Wedge-wire Screens

Measured Screen Dimensions (in.Ib (see Fig. 3) Screen Manufacturer's Open Area, a a2 d hb hr sb st- (%) No. Oesignation Material a, 11 4041slot SSa 0.092 0.040 0.145 0.145 0.167 0.038 0.469 12 60-mil slot 

### ss 0.091 0.040 0.146 0.145 0.171 0.061 0.469 13 100-mil slot 14 80-mil slot ss 0.093 0.041 0.146 0.147 0.170 0.080 0.464 '22.3 30.1 ss 0.093 0-039 0.148 0.145 0.168 0.099 0.467 39.5 35.2 aStainless steel. bTo convert inches to millimeters, multiply by 25.4.

### 96 Screen Reynolds number. The screen Reynolds number (IR) 

### isbased on the unobstructed up

### stream velocity (V), the top width 

### of the trapezoidal screen bars (al), and the 

### kinematic viscosity 

### (u) of the fluid: Va 

### 1 IR=---. 

### Table 3 

### shows the screen properties for the four samples of welded wedge-wire screens that were tested. Pressure drop coefficient correlations. The literature contains results of many investigations of the pressure drop due to flow through fine-mesh screens (Refs. 1-15). The 

### following summary of published pressure drop coefficient correlations 

### is valid for flow normal to a squaremesh, 

### simple-weave, screen made of circular wire. The pressure drop coefficient is 

### a function of 

### the screen wire Reynolds number and the fractional open area of the screen:
Figures 4 and 5 show this relationship 

### as expressed by several authors. The pressure drop coefficient 

### is shown as a function of 

### Reynolds number inFigure 4 for a screen with

### 47.4%open area (Screen 

### No. 3). 

### For Reynolds numbers larger than about 500, 

### the effect of viscous forces 

### is negligible, the pressure drop coefficientbecomes independent of the Reynolds number 

### and 

### is a function of 

### the open area only. is 

### also shown. This 

### range corresponds to intake approach velocities from 6 cm/s to 60 cm/s. 

### It can be 

### seen inFigure 

### 4 that in this range both viscous and intertial forces have an effect on the 

### pressure drop 

### coefficient. The nine curves shown exhibit fairagreement. gives high values in

### comparison to the others. Reference 6 

### gives low values for high 

### Reynolds numbers. The probable range of Reynolds numbers for steam plant intakes
Reference 14

V=60cm/r 

### I 

# I

,--. I I 

## I I 

### %a I



### I1 I 

### I I I ltll I 

### I I I I frIll I I 

### I I 

### I Ill}

~ 10 20 40 60 80 100 200 400 600 800 1000 2000 4000 60008000 SCREEN WIRE REYNOLDS NUMBER,IR =Vd/u Fig. 4. 

### Comparison of Pressure Drop Coefficients Computed from Various Sources in

### the Literature The probable range of Reynolds numbers to be applied atsteam plant intakes for Screen No. 3 

### (47.4%open area). properties. with

### water at60°F corresponds to intake velocities of 6-60 cm/s (shown between the 

### broken 1

### ines). See Tables 7 

### through 3 

### for data and screen
.

### 97

4.

### c

3.5


# - 0 

### ? 3.0 

### >
0 N



# - \ r
II g 2.5
I= 

## w z
u LL W 0 V CL 2.0

1.5 n W (z 3 v, (z a 

## 2 1.0

0.5

0' FRACTIONAL OPEN SCREEN AREA, Q Fig. 

### 5. Comparison of Pressure Drop Coefficients for High 

### Reynolds Numbers asa Function of Open Screen Area. numbers refer to the 

### reference list. The encircled

References 1, 6, 7, and 8 

### seem toyield good mutual agreement. These correlations are: From Reference 

### 1:

with 

### IR 

## I 50 100 

### 150 200 300 f(R)11.44 1.24 1.13 1.08 1.08 e 

### From Reference 6: 

## -5

# I K(6) = 

### 6(1-a)a-3 iR3 

# . From Reference 7: IK(7) = 

### - - 1 

### f(lR) 

### , 

# (.: ) with €2 

## I 50 79 100 

### 126 158200 316 f(W) 

## I -89 .76 .71 -67 

### .63 -60 -57 *98

From Reference 8:

inwhich all lengthdimensions are ininches. Note that the last correlation does not make use ofthe percent open area, but instead uses the screen void fraction (E) and surface area/volume ratio (a). The pressure drop coefficient isshown as a function ofthe fractional open screen area in Figure 5. Note that the pressure drop coefficient increases rapidly forscreens with open areas less than 50%. Again, results from References 1, 6, 

### 7, and 8 seem to be ingood mutual agreement.

RESULTS OF PRESSURE DROP MEASUREMENTS The ten screen samples were mounted atthe end of a flow nozzle through which measured rates of airwere blown for the measurement of pressure drop across the screen. tribution across the 40-cm-diameter (16-in.-diameter) nozzle throat was measured and found to be sufficiently uniformthat no measurably largeerror existed inthe pressure drop due to flow maldistribution. The airdensity was calculated for each test on the basis ofwet-bulb, drybulb, static-pressure and atmospheric-pressure measurements. The airflowwas metered with a sharp-edged orifice installed ina straight section of pipe between the fan and the nozzle. pressure drop across the screen was measured with a differential micromanometer down to the nearest 0.05 mm ofwater column. The flow disThe

As an example ofthe results, the measured pressure drop-Reynolds number correlation for
Also shown inFigure 6 are the head losses to be expected ateach end ofthe' screen No. 5 isshown inFigure6 and compared to the results from Reference 8. There isgood agreement. The pressure drop measurements for all ten screen samples are similar, but are not presented here. velocity range from 6 cm/s to 60 cm/s. to 76 mm, and atthe lower velocities the head drop ranged from 0.3 

### mm to 2 

### mm ofwater for all ten screen samples tested. errors inscreen properties. Screen No. 2 was a nominal 10-mesh screen, according to the manufacturer. Using thisvalue, a nearly50%underestimate ofthe head drop resulted. A close inspectionof the screen sample revealed that the actual mesh was higher than 10 and not square, namely 11 x 12. Using an average value, a much better pressure drop prediction resulted. Therefore, pressure drop isvery sensitive to small changes inscreen geometry. For accurate estimates, actual measured dimensions should be used inpressure drop calculations. Atthe higher velocities the head drop ranged from 13 mm Note inFigure 7, however, the strong effect on pressuredrop of

The measured pressure drop coefficients forthe four samples ofwelded, wedge-wire screens The plots show that as functions ofthe Reynolds number based on the top width of the wedge-wire are shown in Figure8. as the Reynolds number isincreased to a critical value (Rc) of about 500 and 600 for screen Nos. 14 and 13, respectively, the pressure drop coefficient isincreased. As JR isincreased beyond this critical value, 

### IK remains constant, indicating independence ofthe pressure drop coefficientwith respect to Reynolds numbers larger than Rc. 'apparentlywere all conducted at Reynolds numbers larger thanIRc for these screens. Also shown inFigure 8 isthe probable range of Reynolds numbers to be applied atsteam plant intakes with water at60°F. At60 cm/s the pressure drops calculated from the pressure drop coefficients inFigure 8 are 180, 104, 53, and 71 mm ofwater forscreen Nos. 11, 12, 13, and 14, respectively. The results indicate two distinct regions of

### IK dependence on IR.

The tests 

### on screen 

### Nos. 11 and 12
These numbers correspond to intake velocities from 6 cm/s to60 cm/s.

Given a constant screen geometry, independence ofthe pressure drop coefficient with respect to Reynolds numbers larger thanIRc implies that

### IK is a function only of the open fractional area (a)ofthe screen inthis region:K = f(a) 

# . The functional relationship between

### M and CY forwelded wedge-wire screens with Reynolds numbers larger ttian RCis indicated inFigure 5. boundary conditions (IK = 0 ata = 1, iK -f

# - as a -f 0) isexpressed by the equation A curve fit through the data points and satisfying the
K=- 0 044 0-511

### + 

### -- 0.555 forIR t IRc 

# -

a2 a99 5

h 0, 

### aJ \ 

## > N '74 

### a r
II YtLJ 

# -

. 23 

## Y LL LL W 0 v2 

### n 

# -

0 of 0 W 3 v) 

### cn w of off



### a 00 

### 50 IO0 

### I50 

### 200 250 300 

### SCREENWIRE 

### REYNOLDS NUMBER,

### lFt=Vd/u Measured PressureDrop Coefficient for Screen No. 

### 5 (51.0%open area). See Tables 1 through 3 

### fordata and screen properties. The probable range of Reynolds numbers to be applied atsteam plant intakes with

### water at60°F 

### corresponds to intake velocities of 6-60 

### cm/s (shown between the broken lines). Fig. 6.



## I 

# I I

SCREEN WIRE REYNOLDSNUMBER, TR =Vd/v 

### Fig. 7. 

### Measured Pressure Drop Coefficient for Screen No. 2 (42.3% 

### open area). through 3 

### fordata and screen properties. tobe 

### applied atsteam plant intakes with

### water at60°F 

### corresponds to intake velocities of 6-60 

### cm/s (shown between the broken lines). See Tables 7 The 

### probable range of Reynolds numbers

### 100

- .

Screen NO. 12. a.30.1 %



### I 100 200 300 400 500 600 700 800 900 SCREEN REYNOLDS NUMBER, R=Va,/V 

## I I 

## I 

# I I 

# I I I 

# I 

# I I I 

# i 

# I 

# I I 

# I -I

Fig. 8. 

### Measured Pressure Drop Coefficients for Welded Wedge-wire Screens. through 3 

### fordata and screen properties. numbers to be 

### applied atsteam plant intakes with

### water at60°F corresponds to intake velocities of 6-60 

### cm/s (shown between 

### the broken 

### lines). See Tables 1 The probable range of Reynolds

PRESSURE DROP FOR 

### OBLIQUE FLOWS The pressure drop resulting from flow atan angle to simple-weave, square-mesh screens 

### is studied in

### References 2, 3, 9, 

### 11, and 12. Data show that if the flow approaches the screen at an angle 

### (e) normal to 

### the screen, the 

### pressure drop can be 

### estimated correctly using the normal orcosine component of the 

### velocity in

### the pressure drop-Reynolds number correlation. In other words: 

### K(e) =IK(o) 

### cos2 

### e , in

### which IK(8) 

### is the pressure drop coefficientforflow atan angle

### e normal to the screen and IK(o) 

### is the coefficient for

### e = 

### 0, 

### i.e., 

### IK for flow normal to the 

### screen.
different angle. screen, there will 

### be a tangential force on the 

### screen. drop coefficient, a tangential force coefficient (IF) can be 

### defined: Note that if flow enters the screen obliquely it

### also leaves the screen obliquely but 

### ata Also, inaddition to the pressure drop which results in

### a normal force on the 

### In a manner similar to the 

### pressure 

### F=- F 

### @* 1' in

### which 

### F 

### is the tangential force on the screen and p 

### is the density of the fluid. 

### flow angles between 0 

### (normal) and 45", the 

### following tangential force coefficientcorrelation is 

### given in

### Reference 3: 

### For approach

in

### which the 

### angle e is 

### expressed in

### radians. agreement with 

### a limited setof data. our own experiments on pressure drop due 

### to oblique approach flows. This 

### correlation is 

### shown to yield numbers in 

### We have not found any better correlations, nor performed

### 101
PRESSURE DROP THROUGH 

### PARTIALLY, ARTIFICIALLY PLUGGED 

### SCREENS The main problem encountered in

### calculating the pressure drop through screevwhich are partially plugged by accumulation of various kinds of debris and 

### trash 

### is the 

### quantificationof hydraulic properties of the debris. of possible debris sizes and shapes render theproblem quite intractable. simplified approach was taken to gain 

### atleast a measure of insight into possible pressure drop magnitudes forpartially plugged screens. Itwas postulated that the pressure drop could be estimated based solely on the fractional open area of

### the debris plugging 

### the screen. drop across a screen which was plugged 

### to various degrees by uniformly spaced circular rods. The measured pressure drops were correlated with 

### the computed fractional open area of the partiallyplugged screen. Kpp = Ks -tKd(a), 

### inwhich Kpp 's 

### the pressure drop coefficient fora partially plugged screen, Ks 

### is the pressure drop coefficient for the 

### clean screen itself, and Kd(a) is thepressure drop coefficient forthe debris, based 

### on the estimated fractionally open area (a)

### atthe partially plugged screen, The latter, Kd(CL), 

### is 

### computed from the same screen pressure drop formula as 

### the former 

### (KS). For example, using screen No. 2 with a = 

### 0.357 ata flow corresponding to a Reynolds number of 200 

### and the pressure drop equations from References 1 and 7, 

### the following results were obtained: The randomness of 

### the plugging process and 

### the vast variety Therefore, a very

This 

### postulate was tested by measuring the pressure According topostulate, the pressure drop coefficient should be

sfd - m 

### 1

## .ooo 0.500 

### 0.250 

### 0.125 IK 

### 4.3 6.2 

### 10 21 47 Measured IK 

### (Ref. 7) 

### 4.1 5.8 8.9 

### 18 54 IK 

### (Ref. 1) 4.4 6.0 9 22 

### 78 The agreement between the 

### measured and estimated values 

### is reasonably good, indicating that the postulate for pressure drop across partially plugged screen can be used to obtain reasonably accurate numerical estimates. Note, however, thattrash geometries deviating substantially from the circular cylinder shape can be expected toyield differentvalues. A 

### better approach might be to compute the "effective" fractional open area of the screen, based on the open area remaining afterplugging, as ae = 

### a(l-P), in

### which ae

### is the 

### effective fractional open area, a 

### is the fractional open area of the clean screen, and P 

### is the fraction of the 

### clean screen open area that is plugged. The 

### pressure drop coefficient for the partially plugged 

### screen can be estimated from the screen pressure drop formula for the clean screen with ae 

### substituted for a. 

### tiallyplugged wedge-wire screen ispresented in

### Figure 9. 

### Screen No. 14, with 

### an approach velocity of 30 cm/s, was used 

### for the 

### pressure drop coefficient computations. debris" method isdenoted by the solid curve and the "effective a'' 

### method 

### is denoted by 

### the dotted 

### curve on the 

### plates. In Figure 

### 9 it

### is indicated that the "effective a'' 

### method predicts larger pressure drop coefficients than the "separate debris" 

### method throughout the range of plugging. Also indicated inFigure 9 

### are the nearly vertical slopes of the curves forplugging percentages largerthan 90%. 

### P, comparison of these two methods for computing the 

### pressure drop coefficient fora parThe "separate

SCREEN 

### PLUGGING AND 

### FOULING One of the 

### most often-raised questions regarding the use of screenswith

### very small openings 

### is: with 

### such small openings will not the screen plug up 

### and the 

### flow of 

### cooling water stop? In addressing that question, we will 

### divide the screen plugging

### mechanisms into two distinct categories: (1) mechanical plugging due to the 

### impingement of entrapped debris 

### (organicor inorganic) and the 

### formation of a filtermat, and (2)

### biological fouling due 

### to the growth of live organisms thatmay colonize the screeningmedium. In addition, 

### there is 

### the problem of 

### protecting the screening medium 

### from the impact of 

### largedebris that may tearordamage 

### the screens. Currently, 

### we have tests underway to shed some light

### on aspects of the mechanical plugging

There was a continuous flow of water approaching, flowing over, and bypassing the 

### screen The results are necessarily site-specific and seasonal. of a flat, wedge-wire screen sample with 1-mi 

### slotwidth. The 

### approach flow was parallel to the 

### horizontal surface of

### the 46-cm square screen sample and the slutswere arranged parallel to the 

### flow. sample. Measurements 

### were made of the flow-ratethrough the screen and the

### pressure drop across the 

### screen. Most of the

### testingwas performed in

### December 1977 in

### a river-like 

### environment with 

### rapidly varying stage. the debris collected consisted mostly of silt

### and fragments of aquatic vegetation. In this 

### case, Pumping102

3.6

a WtU 3 3.0 0 E 

### ?2.4 2 W W a 0 v) I 1.8 0 J3 0 a IILL

c



## % 1.2 a W a 3 

## 2 0.6 W U a n

0 Fig. 

### 9. Comparison of Pressure Drop Estimates for Partially P1ugged Screens

0 20 40 60 BO IO0 PERCENT OFSCREEN OPEN AREAPLUGGED,P
CLEANSCREEN,Q =0.352 OR 35.2%.SCREENNo.14 TR > IR, V= 30cm/s 

# t

through 

### the screen with

### an average, superficial slotvelocity of about 15

### cm/s continued until an arbitrary head drop-of 1.25 

### m occurred across the screen. backwashed and the testwas repeated. Typical results are shown in

### Figure 10. At

### that point the 

### screen 

### was
The 

### average pumping time between backwashes was about three hours, a1though 

### times varied from as shortas one-half hour 

### to as long as eight hours, depending mostly upon the 

### river stage. High stages promoted rapid plugging. river stage orwhether 

### the 

### river was rising

### orfalling. The firstmethod was to stoppumping and let the bypassing 

### river flow clean the screen for varying durations. from 0.3 

### to 1.0 

### m/s. The 

### cleaning efficiency (c.e.) was based upon the residual head drop (AhR) after cleaning as compared to the 

### head drop across a completely clean screen (Ahc): No 

### trends were found relative to the 

### rate of change of Backwashing was accomplished in

### three ways. The river velocities ranged Washing times of 30, 60, 

### and 300 

### secwere used.

AhR 

### - Ahc 

### c.e. = nh C ut4 A 

### value of zero would denote a perfectly clean screen. the longer washing times, but were 

### notgood (20-200) using this 

### method. reversed pumping through the screen was tried, with 

### slot velocities of about 0.4 

### m/s and 3- 

### minute duration. compressed airwas used to forcewater inthe 

### suction pipe 

### back through the screen with 

### slot velocities of about 1 

### m/s 

### forabout 3 

### seconds. These 

### preliminary tests showed that the most efficient cleaning orbackwashing method was the 

### use of compressed air

### to forcewater out through the slotwith

### a velocity an order of magnitude greater than the 

### suction velocity, and that.this backwashing is 

### essentially accomplished in

### a matter of a few seconds. Another concern is 

### the possibility of a slowly increasing res-idual pressure drop accumuThe 

### cleaning efficiencies improved with
In the third

### method, 40-psi As 

### a second method, Cleaning efficiencies of about 20 

### were obtained. Cleaning efficiencies from 2 to 

### 15were obtained.

lated after repeated backwashing cycles. terms of

### cleaning efficiency in

### Figure 71. a trend 

### towards an equilibrium condition of about 20. most applications. The accumulated residual pressure drop is 

### expressed in 

### The data are still'incomplete, but there 

### seems to be This 

### value should be 

### sufficiently low for

### 103
336.1

336.2

335.s

1.5

1.0

0.5 I

I 

# I -I 

# -+ 

# 1

04P 6P DECEMBER 19, 1977 

### Fig. 

### 10. Typical Results of Plugging Tests inthe

### Field (welded wedge-wire screen, 1-mm slot, 15 

### cm/s slotvelocity)

1 I I I I I I I I I 0 2 4 6 8 IO 12 14 16 18 20 22 24 I



### . 

## __.. .---
~ ~~ NUMBER OF BACKWASHING CYCLES, AIR Fig. 

### 11. Accumulating Residual Pressure Drop After Backwashing104 

### Observation of screen surfaces after a period of use generally reveals dirty-looking screen wires that to the 

### inexperiencedeye may seem like a well-plugged screen, while in

### factmeasurements 

### show that 

### the screen is still quite 

### open and passing water readilywith

### a tolerable pressure drop; Itshould also be noted that long, thin, 

### elongated debris shapes like 

### fibers, grasses, and seaweeds may be relatively easy to keep 

### off a screen with openings 

### so small that the debris isnot partially entrained. and this mat 

### must be frequently removed by moving the 

### screen orby backwashing. The tests 

### so farindicate no major problem in

### accomplishing this task with 

### regard to mechanicdl plugging. 

### tests have yet been made on biological fouling. A 

### filtermat will 

### form on the 

### screen with small openings, No

AREAS OF 

### ADDITIONAL RESEARCH NEEDS 

### More data are needed on the rate of mat.formation on screenswith 

### very small openings. These data will probably be both site-specific and seasonal and will depend on the 

### flow field near 

### the intake. by living organisms. There 

### is a specific need for data on the possible colonization of the screens
More field data are needed on long-term screen washing methods. Such tests 

### must go hand in 

### Data are also needed on the separation of larvae from hand with

### the plugging and fouling tests. the debris mat on the screen. The approach flow into large intakes should be considered carefully to prevent suction of 

### undesirablewater partials, to prevent separation, eddying, and other undesirable flow conditions, and to obtain the specific flow field needed to avoid entrapment of larvae. model tests may be necessary to 

### insure the 

### proper flow field. Physical scade


### There also seems to be 

## a lack of knowledge on 

### the response of larvae of various species to the measurable characteristicsof a flow field such as (1)mean velocities, (2) 

### velocity gradients inall 

### three spatial directions, (3) turbulence intensity, and (4) turbulence scale. If we knew the response of fish to these flow parameters, we could design intakes to obtain specific desir

### able flow conditions and predictable fish response.

REFERENCES 1.

2.


### 3.
4.
5.

7.
8.


### 9.
10. Idel'chik, I. E. 

### 1966. Handbook of Hydraulic Resistance--Coefficients of Locat Resistance and of Friction. AEC-tr-6630. Translated from Russian. Prepared by the 

### Israel Program for ScientificTranslations, Jerusalem, for the U. S. 

### Atomic Energy Commission and the National Science Foundation. Schubauer,'G. B., W. G. 

### Spangenberg, and P. S. 

### Klebanoff. 1950. Aerodynamic Characteristicsof

### Damping Screens. Technical Note 2001. National Advisory Committee forAeronautics. Carrothers, P. 

### J. 

### G., and W. D. 

### Baines. 1973. Forces on Screens of Small Solidity lnclined to a Fluid Flow. Am. SOC. 

### Mech. Eng. Pap. No. 73-WA/FE-20. Cornel!, W. G. 

### 1958. Losses in

### flow normal to plane screens. Trans. Am. SOC.

### Mech. Eng 

### 80:791-799. Collar, A. R. 

### 1939. The 

### Effect of Gauze on the 

### Velocity Distribution in a Uniform Duct. Nat. Phys. Lab. U.K. 

### Rep. & 

### Mem. 

### No. 1867. Wieghardt, K. 

### E. G. 

### 1953. On the 

### resistance of screens. Aeronaut. Q. 

### 4:186-192. Annand, ,W. J. D. 

### 1953. The resistance to airflow of wire gauzes. J. R. 

### Aeronaut. SOC. 

### 57: 141 -146. Armour, J. C., 

### and J. 

### N. Cannon. Chem. Eng. 

### 14(3):415-420. Carrothers, P. J. G., 

### and W. 

### 0. Baines. 1965. Forces on screens inclined to 

### a fluid flow. J. Fluids Eng. 

### Trans. Am. SOC.

### Mech. Eng. 87:116-117. Baines, W. D., 

### and E. G. 

### Peterson. 1951. An 

### investigation of flow through screens. Trans. Am. SOC.

### Mech. Eng. 73:467-480. Taylor, G. I., 

### and G. K. 

### Batchelor. 1949. The effect ofwire 

### gauze on ma71 disturbances in

### a uniform stream. 

### Q. J. 

### Mech. Appl. 

### Math. 2(1):1-29. 1968. Fluid flow through woven screens. 

### J. Am. 

### Inst.

11.105
12. Alsaffar, A. M. 1974. Hydrodynamic effectson flow through screens 

### atintakes. Water
13. Ingmanson, W. L., S. 

### T. Han, H. 

### D. Wilder, and W. T. Myers, 

### Jr. 1961. Resistance of 

### wire
14: Hoerner, S. F. 1965. Fluid-Dynamic Drag. Practical Information on Aerodynamic Drag and
15. Padman-abhan, 

### M., and S. Vigander. 1978. Pressure drop due to flow through fine

### mesh 

### Res. 8:617-622.

screens 

### toflow of water. Tappi 44(1):57-54. Hydrodynamic Resistance. Published by the author. Libr. Congr. Cat. card 

### No. 64-19666.



### screens. J-Hydraul. Div. Proc. Am. SOC.Civ. Eng. 

### (Inpress..)

### BIOLOGICAL AND ENGINEERING CONSIDERATIONS FROM COOLING WATER INTAKES IN THE FINE-SCREENING OF SMALL ORGANISMS

Yusuf G. Mussalli, Edward P. 

### Taft, and Peter Hofmann Stone 8 Webster Engineering Corporation P..O. Box 

### 2325 Boston, Massachusetts 02107

Abstract Fine-screeningof small organisms can be grouped into two concepts: impingement and deterrent. Impingementconcepts involve the collection and removal of organisms with through-flow, center-flow, and dual-flow traveling screens. In evaluating the biological effectivenessof these screens, consideration should be given to species, approach and through-mesh vetocities,mesh opening, impingement duration, debris load

### ing, and type of organismwash system, Engineering considerations include potential for clogging, need for continuous operation of the screen, and screening material. Furthermore, each type of traveling screen has advantages and disadvantages relating to the potential for debris and organism carryover, screening area, screenwell layout, velocity distributionalong screen face, and potential effect on pump performance. Impingement and diversion systems require that collected organisms be returned to the source water body. units. The impingement concept appears to be the most practicable solution for once- through cooling systems. Deterrent concepts, 

### in which the organisms passively drift by a screening device, Transport systemscan utilize either gravity flow or pumping

include infiltration systems such as radial wells, porous dikes, and wedge-wire screens. Biologically, the radial wells and wedge-wire screens

### will cause little impact to small organisms. The porous dike has not been employed for the protection of small organisms todate. Engineering considerations presently limit the use 

### of wedge-wire screens and radial wells tomakeup water intakes with small withdrawals.



### INTRODUCTION Extensive research and development efforts have led to

### the design of fish protection systems which are nowbeing utilized to prevent losses of juvenileand adult fishes at power plant cooling water intakes. developing new technologies,for the protection of egg and larval stages which are normally subject to entrainment in circulating water systems. Due to the small size of such organisms, all protection systems investigatedorproposed to

### date utilize collectionor deterrentmedia with fineopeningssuch thategg and larval formsare physically prevented fromentering intakes. Such fine-screeningcan greatly increase the potential for engineering problems relative to reliableoperation of the coolingwater system. Biological and engineering criteria which should be considered when selectingdesign parameters for

### an intakeutilizing finescreening are discussed. type of screen fora specificsite,screenwell layout, screenmesh size,mesh material,wash systemsand special featuresforprotecting organismsare presented. Recently, attention has been given to extending available technology,or

Criteria for selecting the proper

BACKGROUND The entrainmentof small organisms into cooling water systemshas been a critical and controversial subjectrelative to

### the licensing of power plants. As a result, extensive research
107

### loa
has been conducted to quantify entrainment mortality and to determine the impact of such mortalityon the ecology of the source water body. Large study programs have alsobeen carried out to identify sources of mortality (thermal stress, mechanical injury, biofoul ing control 

### agents, pressure) with the 

### goal of developing power plant design and operating criteria which might act to improve the survival of organisms passing through a cooling water system.



### vent small organisms from entering the cooling water system altogether. While the concept of 

### fine screening for theprotection of organisms atpower plant intakes 

### is relatively new, fine

### mesh screens and microscreens have been used extensively in

### the past for industrial purposes. Of particular interest 

### isthe fact that fine-mesh traveling screens of 

### the center-flow (singleentry, double-exit) and dual flow (double-entry, single-exit) type and drum 

### screens have been utilized formany years atpower plants in

### Europe. operation of fine-mesh screens isavailable. the effectiveness of these European installations in

### excluding fish eggs and larvae. nary biological data on fine-screening have been obtained 

### from recent studies in

### the U.S. 

### These studies arethe subject of other papers inthis 

### proceedings. broad overview of research efforts todate such that common engineering and biological considerations can be identified, and a basis for future 

### studies can be developed.
into two categories based on their mode of action: impingement concepts, inwhich organisms are physically impinged and removed from a screeningmedium, and deterrentconcepts, inwhich the velocity through the screeningmedium 

### is designed tobe 

### low and the screening device 

### is oriented in

### a natural current such thatorganisms driftpassively by the device. lattercategory would appear tooffer a better solution to entrainment problems, application 

### is presently limited 

### tomakeup flow rates of closed-loop cooling systems, and relies on 

### the presence of specifichydrographic and environmental conditions. Their practicability 

### is, therefore, sitespecific. Impingement concepts, on the otherhand, utilize more conventional equipment 

### which may be practicable atmany sites, particularly for once-through cooling, provided that the 

### organisms of concern can withstand the impingement and removal process. Therefore, it is

### evident that both concepts have engineering and biological advantages and disadvantages. is 

### a discussion of these concepts, their present stage of development, and the research needed toresolve 

### inherent design problems such that they may be applied to power plant intakes with 

### an acceptable degree of 

### reliability. Recently, preliminary studies have been initiated to develop intake designswhich will 

### preTherefore, information on the design a_nd However, 

### no information 

### is availablerelative toPrelimiTkerefore, this paper presents a

The various fine-screening devices orsystems investigated to date can be 

### broadly grouped

While 

### concepts inthe



### The following

IMPINGEMENT CONCEPTS The 

### impingement-concept categorypresently includes through-flow traveling screens, 

### centerflow (single-entry, double-exit) screens, dual-flow (double-entry, single-exit) screens, and various modifications of these offered by different screen manufacturers. All 

### screens incorporate a screeningmedium with 

### sufficiently small openings to retain the smallest organism of interest

# - BIOLOGICAL CONSIDERATIONS To 

### date, there is

### only one operating fine-screening installation inthe 

### United States from
These operatecontinuously ata speed of 4.3 m/min 

### (14 fpm) and screen which biological data have been obtained. pany's Barney Davis Station in

### Corpus Christi, Texas, which utilizes four center-flow screens with 

### 1.0-mm nylon mesh. 

### a total flow of 22 

### m3/s (757 cfs). corresponding toa through-mesh velocity of 0.52 

### m/s (1.7 fps). report that initial survival of fragile fishes such as Gulf menhaden (Brevoorti~ patronus) 

### and Bay anchovy (Anchoa

### mitchiZZi)measuring 18to 86 mm 

### inlength 

### is high afterthey arewashed from the 

### screens. While latentmortality studieshave not been conducted, these preliminary 

### results indicatethat impingement devicesmay offer a viable method 

### forpreventing entrainment of 

### small organisms. This installation 

### is Central Power and Light 

### ComThe 

### gross velocity atthe screen face 

### is 0.24 

### m/s (0.78 fps) Murray and Jinnette (1978)



### Several laboratory and field studiesalsodemonstrate the

### potential forhigh survival of 

### ichthyoplankton following impingement. sored an evaluation of a fine-mesh through-flow traveling screen atthe Indian Point Generating StationUnit 

### 1 on the 

### Hudson River 

### (Ecological Analysts, 

### Inc., 1977). One 

### traveling water screen was backfitted with

### 2.5-mm nylon mesh and modified with 

### fish buckets, a low-pressure spray header and a collection trough on the 

### rear side-ofthe screen. Collection efficiency studies

### were conducted with

### 72- 

### and 14-day-old post-yo1 k-sac hatchery striped bass (Morone smitilis)with

### mean standard lengths of 7 

### to9 mm. 

### Survival estimates were obtained with

### wild fish, primarily late post-yolk-sac (15mm MSL) 

### and earlyjuvenile 

### (19

### mm MSL) 

### striped bass. approach velocity was approximately 0.12 

### m/s (0.4 fps) and the screen travel speed was 3 m/min (10 

### fpm). retained by the

### 2.5-mm mesh. 

### In 1977, Consolidated fdison Company 

### of New York sponIn all 

### tests, the screen The 

### results of these studies showed that 7- to 9-mm larvae were 

### not effectively Itwas concluded that 10- to 18-mm 

### larvaemay be the smallest Size

### that can be collected on mesh 

### of 

### this size. post-yolk-sac larvae washed from the screen were 68 and 

### 47 percent, respectively.' Initial and latent survival estimates of earlyjuveniles were 100 and 

### 88 

### percent, respectively (Ecological Analysts, Inc., 1977). The 

### Indian Point study results are relativelyconsistent with those obtained in laboratory and 

### field studies conducted by the Tennessee Valley Authority (Tomljanovich 

### etal. 1977). of eleven fish species were tested 

### ina flume containing various screen panels to determine the mesh 

### sizeneeded toretain the larvae and 

### the mortality associated with 

### impingement. ranging from 

### 0.5 to2.5 m

### were evaluated atwater velocities of 15, 

### 31, and 46 cm/s (0.5, 

### 1.0, and 1.5 fps). from 0.5 

### to 16minutes to determine the effect of impingementduration on retention and 

### mortality. Tomljanovich et

### al. (1978) 

### has presented 

### an excellent sumnary of the results of these studies. Several conclusions reached from the research have important implications relative to the develop

### ment of fine-screening design criteria for power plant application. First, itwas found that the 0.5-m 

### mesh was the only screen size that retained nearly 100 

### percent of

### the smallest fish tested (average body depth 1.0 

### to 

### 1.4 mm) and that with mesh sizes larger than 0.5 

### mm, retention was directly related 

### tobody depth. may be necessary toutilize 

### a mesh size of 

### 0.5 

### mm to

### adequately protect larvae despite the fact that they may have body lengths as long 

### as 7.0 

### mm. The effects 

### of screening to such a fine level must be carefully considered relative toincreased debris clogging potential. In addition to the engineering problems which clogging causes, debris loading on a screen could result in conditions which would decrease the survival potential of impinged organisms. area decreases and 

### through-mesh velocity increases. Therefore, 

### atsiteswhere debris loading is medium or heavy, actual through-mesh velocities will exceed the design velocity, possibly causing reduced retention and increasedmortality, as shown by Tomljanovich etal. (1978) for several species. This problem can be minimized by designing the screen to operate athigher travel speeds when necessary 

### toreduce the degree of clogging per unit area of mesh over time. Further, organisms may become entrapped by, 

### or entangled 

### in, 

### the debris itself. This could lead to direct injury, but

### also implies that

### debris should be returned 

### tothe source water body along with separated organisms (assuming a dual-spray system isbeing used) if it is

### found that a substantial portion of the organisms reside in the debris and cannot be effectively separated from it. 

### Initial and latent (96-hr) survival estimates of late

Larvae Mesh sizes Test fishwere impinged on the different screen meshes for varying lengths of time

Therefore, depending on the species present ata specific site it

As a screen clogs, the open

ation among limit Tom1 janovich etal. (1978) 

### also found a strong inverse relationship between impingement dur

### Again, such 

### a requirement could necesand survival. While the duration which resulted inhigh 

### latent mortalities varied widely the different test species, immediate survival data indicated that itmay be desirable to the impingement time to approximately four minutes. sitate high-speed, continuous screen operation. larval survival cannot be made 

### on the basis of the preliminary fine-screening experiments conducted 

### todate. However, itis likely 

### thatcontinuous operation of fine-mesh screens will be 

### required during periods of peak larval abundance, and 

### the engineering implications of

### such operation must be

### considered. Naturally, generic design criteria for maximizing

In conclusion, from a bi.ologica1 viewpoint, itwould appear that

### theconcept of impinging and 

### removing larvae from fine-mesh traveling screens with 

### relatively high survival 

### is a viable one hdhich warrants further investigation. However, utilization of fine-screens may create engineering problems which must be identified and resolved to ensure reliable operation, as discussed below. Since the preceding discussion addresses the biological aspects of impingement concepts ina generat manner, additional biological considerations pertaining to specific screen designs will

### be brought forward inthe following discussions.
ZNGINEERING CONSIDERATIONS The available biological data 

### on fine-mesh screening indicate that the 

### concept of impinging ind 

### removing small organisms through the use of traveling screens appears towarrant further investigation. if traveling screen issuperior toothers relative 

### topotential stress and 

### mortality incurred by 

### rganisms. lisadvantages of specific screen types can be identified, as well as inherent features of each rhich might act toenhance survival of impinged organisms. Sufficient experimentation has 

### not been conducted to

### determine whether one type However, generic engineering considerations in fine- screening and advantages and

!enera1 Considerations The use of fine screens has many engineering implications relative to clogging, continuous ,peration, type of 

### spray wash system, and 

### type of screening material. Due to the small openings as small as 0.5 mm) 

### of fine-screening medium,.these screens will clog much faster than the con- -entional9-mm (3/8-in.) screens currently in

### use atpower plant intakes. A 

### solution to this ncreased clogging potential isthe use of one ormore sets of trash racks upstream of the fine creens. These racks would 

### have clearopenings ranging 

### from 3.8 

### cm (1.5 in.) to 12 m 

### (0.5 

### in.)110 depending on the type and loading ofthe debris. present, a traveling bar or coarse screen, (which ismechanically similar to a through-flow screen) utilizingbar spacings ormesh openings as small as 12 mm (0.5 in.) could be installed between the fine-screen and the coarse trash rack to reduce the debris loading on the fine-mesh screen. (1 in.) to38

### mm (1.5 in.), equipped with automatic raking equipment, could be utilized.
should be capable ofoperating continuously ata low speed ofabout 0.3 m/min (1.0 fpm). on European experience with fine-screening, the following screen speeds are recommended: differential head across the screen of 10 cm (4 in.), a screen should be capable ofoperating at a speed of 3 to4 m/min (10 to 14 fpm). screen should operate ata speed of6 to8 m/min (20 to28 fpm). Because clogging isrelated tothe type and loading of debris at specific sites and because littleexperience exists inthe United States, prototype evaluations should be conducted to determine the degree ofcoarse screening required upstream of the fine-screen, rack spacings, and screen travel speeds which would ensure reliable operation. Bench tests and mathematical models (Saffranand Kormanick 1976) can be used todetermine the hydraulic capacity of a fine-mesh screen. Also, full-scale tests could be conducted ata specific s i t e u t i l i z i n ga screen 0.3- to 0.6-m (1.0- to 2.0-ft) wide prior to installation of a complete screening system, toevaluate the abilityof the system tohandle the debris loading present atthat site. Continuous screen operation can result insubstantial wear ofthe chain flex joints and the bearings and bushings. Therfore, since continuous operation isrequiredwith fine-mesh screeni?g, the traveling screen components should be upgraded to prevent excessive wear. The utilization of heavy-duty chains, rollerbearings atthe head shaft, "stoody" bushings atthe foot shaft, light-weight components, and provisions for proper slack tensioningwillall help to reduce operational problems and maintenance requirements (Mussalli etal. 1977). To reduce the clogging potential and the need for continuous operation throughout theyear, traveling screens could be fittedwith easily replaceable screen baskets ofdifferent mesh size. Inthisway, fine mesh could be utilizedonly during periods of larval abundance, while coarser, 9-mm (3/8-in.) mesh could be used during the remainder of the year. are inthe process ofdeveloping snap-on or insertable screen panels for this purpose. Incases where stringydebris such as grass is
Similarly, formedium debris loading, a stationary rack with bar spacing of25 mm Furthermore, toensure that sudden clogging would not overload the drive motors, screens Based ata Ata differential of 15 to 20 cm (6 to8 in.), the

Several screen manufacturers
A final consideration infine-screening isthe type of screening material used. There are presently four types available: oblong (smooth-top), and wedge-wire oblong. The cost per square foot ranges from $1 for the synthetic and $5 for the smooth-top to $25 for the wedge-wire. Screen liferanges from 3 years for the synthetic to 10 to20 years for the smooth-top and wedgewire. duringwashing. Inlarval protection designs todate, the synthetic square mesh has been used in once-through traveling screen applications, the wedge-wire insubmerged, makeup water intakes, and the smooth-top inexperimental flumes. Inselecting a mesh type, consideration should be given tothe different characteristicsof the meshes. From an engineering viewpoint, ease of debris removal and the support bracing required behind the mesh are also factors tobe considered. Biologically, the smoothness ofthe material, the shape of the mesh openings, and the percent open area are factors which will influence organism retention and survival. percent open area should be above 50 percent to provide adequate hydraulic efficiency for the finemesh. supports, and fishand debris buckets or lipsshould be considered. screen area by 15 to20 percent. woven metallic square, woven synthetic square, woven metallic Each has advantages and disadvantages.
The synthetic mesh can puncture and isflammable, while the metallic square mesh fatigues

Hydraulically, the Also, incomputing through-mesh velocities, the area occupied by the basket frame, This could reduce the gross
Screen manufacturers presentlyofferfront-wash, back-wash, and overhead spray systems for Indealingwith fish debris and organism remova7. there are varying advantages and disadvantages associatedwith each type. larvae, screens using any ofthe spray systems would have liftingbuckets attached toeach panel tocontain the organisms inwater during travel. sprays--one torinsethe screen mesh down intothe bucket and a second toclear the bucket. Therefore, organisms could be exposed totwo wash jets. the bucket are poured out onto the mesh as the screen basket passes over the head shaft; therefore, a gentle spray isrequired towash organisms offof the mesh. The overhead spray design, used on the center-flow screen, isperhaps betterthan the others since there isa good chance that organisms contained inthe liftingbuckets will be spilled by gravity intothe collection trough priortoencountering the spray wash.

source water body. after itclears thewater surface. likelythat much of the impinged debris will be washed down along with the organisms. Froman engineering viewpoint, they are similar. Biologically,
The front-wash system requires two 7ow-pressure Inthe back-wash design, the contents of

With allthree spray systems, itmay be desirable to returnorganisms and debris back tothe Since larvae are very small, they can remain impinged 

### on a traveling screen This necessitates cleaning the entire screen face. Itis Therefore,111

inthe interest ofprotecting the organisms, the entire contents ofthe wash water should be returned tothe source water body. Through-flow Screens The through-flow traveling water screen isthe most commonly used screen inthe United States. Itshould be pointedout, however, that there isa potential for debris carryover. Further, careful consideration has tobe given tothe potential for uneven velocity distribution along the screen face due to the influence ofpumps, bafflewalls, and intake configuration. The through-flow screen can be fittedwithfine-mesh screen material and upgraded forcontinuous operation, as previously described, inorder to handle both debris and organisms. For larval protection, the through-flow screens would be modifiedtoincorporate liftingbuckets on each screen basket tocontain these organisms inwater during screen rotation. the liftingbuckets, low-pressure sprays would be added towash organisms from either the front or the back ofthe screen (Mussalli etal. 1977), as disc-ussed previously. Another modificationofthe through-flow screen design which might be considered for larval Inconjunctionwith

protection

### is angling of the screen such that motileorganisms can be guided toa bypass. Numerous studies with fishdiversion devices such as louvers and angled screens have shown that these devices can be very effective inguiding juvenile and adult fishes tobypasses (Schuler and Larson 1974; Taft and Mussalli 1977; Taft etal. 1976). been evaluatedtodetermine their potential for diverting fish larvae, the 100-percent guidance efficiencies observed withjuveniles as small as 25 mn (Taft and Mussalli 1978) may indicate that earlier lifestages could also be diverted by such screens with fine mesh. nonmotileeggs and early larvaewould impinge on the screen, with the exception ofthose which happen toenter the diversion system on the bypass side. tocollect these small organisms inthe same manner discussed previously. All organisms capable of guiding on the fine-mesh screen would be diverted toa bypass. While angled screens have not yet Naturally, Therefore, the screens would be designed

Atthis time, it isnot possible todetermine the age (size) atwhich larval fishmight be diverted by an angled, fine-mesh screen. Naturally, the ability toguide along a screen will be influenced by environmental and hydraulic conditions and will vary between species. However, evidence that larval and early juvenile fishcan guide along angled screens has been reported by Pavlov and Pakhorukov (1973) ina review of the fish protection research which has been conducted inthe USSR. screens inlaboratory and full-scale studies. leads toa fish bypass and utilizes a moving water jetdevice for cleaning. conical screen (Fig. 1) which leads toa central bypass and also has a water jetcleaning device which rotates around the periphery of the screen. water jets for cleaning screens may not be reliable for power plant applications. the fixed and conical screens withwater-jet cleaning have been used for irrigationsystems or large-scale test facilities.
efficienciescan be achieved. Inone study, mosquitofish (Gambusia sp.) 10 to 40 mm longwere guided very effectively toa bypass over a range of hydraulic conditions. Through-mesh screen velocity varied from 0.15 to0.40 m/s (0.50 to1.3 fps) and the amount ofwater drawn intothe bypass ranged from 1 to 10 percent ofthe total approach flow. With a through-mesh velocity of 0.15 m/s (0.5 fps), 88.7 and 97.6 percent ofthe fishwere divertedat bypass flows of2 and 10 percent, respectively. at 1 and 10 percent bypass flows, respectively. were divertedwith a 10 percent bypass flow. Therefore, guidance efficiencywas affectedby approach velocity and bypass flow. However, under all conditions, the efficiencieswere high (greater than 75 percent). Additional laboratory studies with roach (RutiZus mtiZus fZuviutiZis) showed similar results, with guidance efficiencies as high as 96 percent. ments, itwas noted that the best guidance was achieved when the approach and bypass velocity were equal. One final investigationof the angled stationary screen design isreported by Pavlov and Pakhorukov (1973). 16 degrees tothe approach flow was evaluated at a fish hatchery in1968 and 1969. showed that larval fish (species not given) less than 14mm longwere not effectively guided, but larger fish were a71 diverted toa bypass. Laboratory and large-scale studies of conical screens with internal bypasses have also shown highfishdiversion efficiencies (Pavlov and Pakhorukov 1973). Experiments with several species measuring 9.5 to50 mm in7ength have shown very effective guidance along model and full-scale conical screens when the screen mesh (1 to3 

### m>was angled 8 to 12 degrees tothe approach flow with approach velocities as highas 0.9 m/s (2.95 fps). Inone study, verkhovka, perch, and bitterlingwere heldfora minimum of48 hours following testing for determination of latent These studies investigated the effectiveness of two types of fine-mesh diversion One type isan angled, stationary screen which The second type isa Itshould be pointed out, however, that underInthe USSR,

Results of studies with the angled stationary screen design have shown that high diversion

Ata velocity of 0.25 m/s (0.82 fps), 75.8 and 96.1 percentwere diverted At0.40 m/s (1.3 fps), 79.8 percent of the fish
During these experiReducing the bypass velocity caused a drop inefficiency of up to 28 percent.
A fine-mesh screen (1.0-mm mesh), 12.6 

### m (41.3 ft)long set atan angle of Results112

mTmw CONICALSCREEN 

### Fig. 1. Conical Larval Diversion Screen. From Nikonorov and Me1'nikova (1 974).
mortality. mortality. In conclusion, it

### would appear from the 

### results of the Russian investigations that 

### the potential for guiding larval and juvenile fish as small as 10

### nun long with 

### fine-mesh angled screens 

### exists. Screen angle, approach velocity and approach-to-bypass velocity ratio appear to have the 

### greatest influence on guidance efficiency. Since screen angle and flow velocity affect the overall sizeof a screen well ata given flow rate, futureefforts should be concentrated on A 

### optimizingthese parameters with 

### consideration toboth biological and engineerin possible layout fora once-through larval diversion screenwell flow rate of 43 

### m /s (1500 

### cfs) is shown in

### Figure 2. 

### Mortality among verkhovka averaged 8 

### percent while the other species displayed no



# ! concernsCenter-f 1 ow Screens As 

### shown in

### Figure 3, this 

### screen 

### is set parallel to the 

### approach flow with

### water entering a central entrance port and exiting through both the ascending and descending screen faces. screen has an overhead spray system which 

### washes debris intoan internal trash trough. The 

### screen baskets areelliptical and the overall screen assembly is

### oval. screen lengths (front toback) range from 1.2 to4 

### m (4 

### to 13 

### ft), corresponding to approach channel widths 

### from 2.5 

### to 5.0 m (8

### to 16.5 

### ft). bel

### ow: 1. The Commercially available The advantages of this 

### screen are summarized
Since all water is screened internally, there is 

### no possibility of debris carryover, 

### i-e., debris cannot enter the

### cooling water system without passing through the

### screen.

### 113
BYPASSAND TRANSITION

SECTION SCREENWASHPUMPS

TRASHBASKET(TYP)

ICINGDIFFUSER

0 10 20



# * SCALE(ft) SECONDARYBYPASS DRIVINGPUMP(TYP)
Fig. 2. Angled Screen Larval Diversion System

FISH BUCKET ATTACHED TO SCREEN 

## ---____ I 

# 7-1 !1

,/ liD 

## I

,- SECTION A .SH

Fig. 3. Center-flow Screen. Courtesy of Passavant Corporation.

### 114

2. 

### For a given screen width, a larger screening area isavailable than with 

### a flatpanel, through-flow screen. This isdue tothe fact that both the 

### ascending and descending screening 

### faces are used for initial debris removal and 

### that the screen baskets are elliptical rather than 

### flat. designs shown in Figure 4 provide approximately 60 and 110 percent more screening area, respectively, than a flatbasket. screeningwater for the following reasons. circular baskets to each other (Fig. 31, 

### the uppermost portion 

### of the baskets is not very effectiveinscreening water. This results 

### in

### a reduction of screening area of approximately 10

### percent. Second, for the protection of organisms, itwould be desirable to fit each screen basket with 

### a bucket as shown 

### inFigure 

### 3, to hold 

### 5 cm 

### (2in.) of

### water. ing 

### off the lower basket area in this way would 

### reduce the screening area by 20 

### percent. Therefore, with

### a bucket added to each basket, the overall screening area of a semicircular basket may be only 12 percent greater 

### than thatof a flatbasket. Various basket shapes are available; the semicircular and involute However, this additional area 

### is not fully available for 

### First, due 

### tothe close proximity of the semiBlock3. 

### As gu 4. 

### As 

### as 5. Th . i..



### Fig. 4. 

### Comparison of Basket Types PANEL



### designed, the screen has adequate sealing between baskets and between the baskets and the des 

### tominimize the passage of organizms without additional modification. designed, the screen can withstand frequent or continuous operation due tofeatures such head shaft roller bearings and 

### heavy-duty chains.

increased screeninq area described above allows for 

### a reduction in

### the width and/or depth of

### the screenweli structure. Additional design considerations of the center-flow screen are 

### as follows: 1.

2.

3. 

### While it ispossible to achieve low screen.face velocities by increasing the length and width of the screen, velocities 

### atthe entrance port would be higher than the approach velocities tothrough-flow screens. Thus, the

### advantage of increased screening area and the resultant increase in flow capacity may cause a higher entrance velocity which could increase entrapment of fishwithin the screen. For example, at the previously described Barney Davis Station, the approach channel and screen face velocities are only 0.23 

### and 0.24 

### m/s (0.77 

### and 0.78 

### fps), respectively. However, the entrance port velocity 

### is approximately 0.56 

### m/s (1.86 fps). In general, low entrance port velocities, such 

### as0.30 

### m/s (1.0 

### fps), could be achieved by 

### using shorter screens (i.e., lower flow capacity per screen); however, reduction of the flow per screen would necessitate the use 

### of more screens and, therefore, a wider intake structure for a given plant flow. It isdoubtful whether the ascending side, which may be 

### partially clogged, would screen water with equal efficiency as the cleaned, descending side. inthe

### screen area of the ascending screen face should be assumed. ered when establishing design criteria for prototype installations. Due to the

### angle atwhich the approach flow streamlines enter the screen and to the presence of discharge ports on the downstream sides of the screen, the velocity distribution across the

### screen face is

### uneven. Therefore, from a fish protection viewpoint, average design velocity values should not be used. organisms will be 

### subjected to through-mesh velocities in

### excess of the 

### design velocityFurther, the additional influence 

### of debris clogging on velocity distribution should be 

### considered. Consideration should also be given to the fact that

### organisms impinged 

### near A 25 

### to 50 

### percent reduction This 

### should be 

### considRather, it

### should be assumed that many

### 115
the surface of the descending face will be subjected to changing velocities as they travel around the baskets in the lower arch and 

### up 

### tothe overhead spray wash. will experience the maximum impingement duration possible. Water exiting the screen faces discharges from the side ports asjets. patterns created inthe pumpwell could affect pump 

### performance. Research Laboratories 1974a) have been conducted 

### todetermine the effect of 

### a center-flow screen 3.0-m (10 

### ft)long on a vertical wet-pit circulating water pump. 

### considered for installation in 

### a bay 5.2 

### m (17 ft)wide with 

### a design capacity of 

### 9 m3/s (320 

### cfs). center portion of the bay between the back wall of the screen and the pump (Fig. 

### 5). was due to thejet action of the water exiting the screen faces along the walls of the intake bay. 

### to occasionally pull 

### air into the pump 

### bellmouth. Further, the flow was not evenly distributed around the entrance to 

### the bellmouth. The intensity of these flow characteristics was observed to increase as the screen assembly location 

### was moved from 9.75 m 

### (32 ft)to 8.5 

### m (28 ft)

### to 5.5 

### m (18ft)from the pump center-line. To 

### use 

### the screen 

### ata distance of 9.75 m 

### (32 ft)

### or less from the pump 

### would have required a special baffle (Fig. 6) to streamline the flow patterns 

### tothe pump 

### bellmouth. tested; thefinal baffle design selected for this application 

### is shorn 

### in Figure 

### 7. shown 

### inFigure 5, a screen-to-pump distance of 14.6 

### m (48 ft)would have eliminated the need for the baffle. By comparison, utilizing a through-flow screen, with 

### the same flow rate, would have required a distance of only 7.6 

### m (25 ft). screen-to-pump distance 

### is

### touse horizontal 

### orvertical dry-pit pumzi 

### which, because of the design of the inlet tothe pump suction, are less sensitive to fiow disturbances than vertical, wet-pit pumps. features which can affect screenwell layout and pump 

### operation. These organisms
4. The nonuniform flow Model studies (Alden The screen was Test results indicated that a zone of 

### reverse flow was established 

### inthe This



### Eddies were active 

### inthe back corners of the pump 

### bay 

### and were strong enough

Several baffles were designed and As 

### was Another means of reducing the Therefore, itcan be seen that the center-"low screen has design

tP 

### SURFACE 

## FLOW PATTERNS /-CENTER FLOW SCREEN I

IIt I I I I I I It J 

### FEET 40 30 20 10 6 0 85.6 80 70 60 50



### - V 

### -- 

# I IiI

'i, ELEVATION-SECTION 

## qC FEET 6.5

50 a5

-7.0 -10.0

-21.0

Fig. 5. 

### Pumpwell Model with Center-flow Screens (1 ft= 0.305 m). 

### Courtesy of Alden Research Laboratory..116

CENTER 

### FLOW SCREEN FEET 

### SURFACE FLOW PATTEZNS GU,DE 

# rWALL 

## b
85 5.O
0 5.0 8.5 

### NIFORM

I1 I I I I’ If I1 J 40 20 17 10 6 0 50 BAFFLE 

### FEET ’O

# )- 85.6 80 70 60



# 1 ahl=l.O’

CHANNEL ‘p 

### END WALL 

### ELEVATION-

### SECT1ON

# qc

Fig. 6. 

### Pumpwell 

### Model with

### Center-flow Screen and Baffle (1 

### ft= 0.305 m). 

### Courtesy of

### Alden Research Laboratory.

Fig. 7. 

### Baffle Design 

### (1 in. = 2.54 

### cm)117
5.

6. The entrance portofthe center-flow screen isdesigned such that a contractioneffect occurs which influences the distribution offlow (and velocity) across the screen. As shown inFigure 6, guidewalls can be added tominimize the contraction effect and increase the effective use offlow through the full surface of the screen. entrance port increases with depth, the guide walls should be tapered inthe vertical plane tomatch the port. The potential impingement time on a center-flow screen islonger than on a through-flow screen ata given travel speed. the descending face atthewater surface and iscarried through the water column before being liftedto the overhead spray removal system. ment time has been identified for important species, the travel speed ofa center-flow screen may have tobe greater than that of a through-flow screen. Since the width of the

Maximum travel time occurs when an organism impinges on Therefore, ifa limitation

### on impingeDual-flow Screens
center-flow screen and, accordingly, has similar advantages and disadvantages, as summarized briefly below: 1- 2. The dual-flow (double-entry, single-exit) screen (Fig. 8) issimilar inconcept to the

Debris cannot carryover intothe cooling water system. Because two faces are utilizedininitial screening water, there isa greater screening area available fora given screen width than with through-flow screens. increase inscreening capacity isnot directly proportional tothe increased area since the ascending side isnot as efficient inscreeningwater, as discussed previously for the center-flow screen. The flow distribution, and therefore the velocity distribution, along the screen face is not uniform. The flow patterns to the pump will be non-uniform. tories 1974b) for a 9-m3/s (320-cfs) vertical wet-pit pump, using a dual-flow screen 2.6 m (8.5 ft)wide, indicated that the screen should be located ata minimum distance of 11.6 m (38 ft) from the pump center-line when used 

### in conjunction with a baffle, as shown in Figure9. For the purpose of fine-screening at intakes there appears, at this time, tobe no engineeringadvantages tousing the dual-flow rather than the center-flow screen ina screenwell arrangement. design of the wash collection system isbasically the same as with a through-flow screen, potential mortality associated with screen washing would be comparable. A variationof the dual-flow screen, known as the No-well arrangement, isshown inFigure 10. are.presently operating atpower plants inFlorida. struction advantages and may have biological benefits. tothe screen via a transition and turningvanes, the need for a typical screenwell iseliminated. This results incost savings related toexcavation and concrete. however, has applicationsonly inwarm climates toavoid problems associated with icing.
free passage of fish inthe resulting low-velocity areas. Further, the through-mesh velocities could be kept low enough toallow larval avoidance. modifications would be requiredtopermit utilizationof fine-mesh. To ensure reliability during continuous operation, heavy-duty components would be required. Adequate sealing between screen baskets and between the baskets and guides would have tobe incorporated tominimize the loss of organisms inthese areas. Finally, a low-pressure spray system would be needed to gently remove organisms from the screen and liftingbuckets, as previouslydiscussed. However, the

3.
4. Model studies (Alden Research LaboraThe former has less screening area due tothe flat panel design. Further, since the

Several screening installationsof the No-well design, utilizing 

### 9-m (3/8-in.) mesh, This arrangement has obvious cost and conBy connecting the pump suction directly This arrangement,
No-well screens could be installedwith suitable distances between them to allow for the However, as with other screens, design



### . Organism Transport Organisms which arewashed from all types of screens must be returned to the source water body ina carefully designed transport system. lifted, washed intoa bucket, and therefore can be returned to the source water body by gravity transport systems. a liftbasket or a non-clog pumping unit, such as a jet pump, to return the organisms (Mussalli and Taft 1977). For the impingement concepts, organisms are With the diversion schemes, the organisms enter a bypass and would require

### 118

I I I I STEEL FRONT PLATE 

# /

SEAL

SCREENEDWATER Fig. 8. 

### Dual-flow Screen. Courtesy of

### Brackett.

FEET 

### SURFACE FLOW PATTERNS qP 

### r DUAL-FLOWSCREEN 8.5 

## F,

~~ 5.0 8.5

It I I I I I I II 1 856 BO 70 60 50 40 30 20 10 6 0 FEET



### ELEVATION-SECTION 

## Qc

# HLg 0.5'
Fig. 

### 9. 

### Pumpwell Model with 

### Dual-flow Screen and Baffles (1 ft= 0.305 

### m)- Courtesy of

### Alden Research Laboratory.119

SCREENBRACE

MLWEL. 

### (3-0''
ELWEL.5'-0'

FEXCAVATION EL. 24""
Fig. 10. No-well Screen Intake

In general, buckets and pipes should be smooth and sized to avoid high velocities. tions should be gradual and elbows should be long-radius to avoid undesirable velocity conditions. TransiFinally, valves and meters should not create obstructions 

### inthe flow. There islittleexperience 

### intransporting larval fish, and therefore specificcriteria cannot be identified. can be used 

### as a guideline for furtherresearch. However, data from live-sampling gear, such as various types of pumps,

DETERRENT CONCEPTS 

### Fish deterrent systems have received attention due to the fact that they act toprotect


### Atpresent, two types of designs arebeing considered for larval exclusion: organisms with 1ittleor no handling. Conceptually, these systems are designed and/or oriented insuch a way that organisms with 

### littleor

### no motility can be passively deterred form entering an intake flow. infiltration systems, such as radial wells and porous dikes, and cylindrical, wedge-wire screens Biological and engineering considerations inutilizing such systems are discussed below.
BIOLOGICAL CONSIDERATIONS The radial well 

### is an available system which can be utilized where geological conditions are suitable. however, their 

### use is limited to low-capacity intakes.
power plant intakes. prevent the passage of fisheggs and larvae. motile, they drift passively ina current and would, therefore, be subject toentrainment into the dike 

### unless 

### a fine filteringmedium 

### is placed on the outer surface and an adequate ambient flushing flow existed to carry the organisms away from the structure. motile organisms 

### must be screened 

### attheouter surface boundary rather than within the dike, since any organism which penetrates thisboundary will ultimately be lost regardless of the Operation of radial wells will 

### result inlittle impact to small organisms;
The porous-dike concept has never been employed for the protection of small organisms at The primary biological concern with thedike relates to its ability

### to Since these early life stages are essentially nonItis believed that non-120 

### screening capacity of the 

### media located in

### the interior of dike. filtering media atthe outerboundary could createengineering problems in terms of protecting the dike

### from wave forces. screen all of 

### the life stages desired due toengineering design limitations.
sented by Hanson 

### etal. (1978). Itwould appear that such screens would be effective in

### preventing 

### the entrainment of fish eggs and larvae provided that the screen slot 

### size is 

### small, the through-slot velocity 

### is low, and a relatively high velocity cross-flow exists to carryorganisms around and away from the screen. Accordingly, the 

### biological effectiveness of wedge-wire screens may be site-specific in

### cases where they are intended to protect non-motile organisms. However, locating the fine Therefore, it

### may be found that the dike cannot be 

### designed to
The results of biological research on the use of cylindrical, wedge-wire screens arepreENGINEERING CONSIDERATIONS Radial wells and wedge-wire screens are commercially availablesystems which, todate, have been successfully applied tomakeup water intakes, while the porous dike 

### is in

### the developmental stage and has not yet been 

### utilized. Experience indicates that maximum capacity of a single radial well is

### limited to about 0.6 

### to 1.25 m3/s 

### (10,000 to 20,000 gpm). 

### For a once-through application, given 

### a suitable aquifer, about 30 

### to 45 

### km (20

### to 30 mi) 

### of shoreline could be 

### required to supply 30 

### to 60 

### m3/s (500,000 

### to 1,000,000 gpm) of cooling water. This

### consideration and the 

### associated costs of pumps and a largepiping network would rule out 

### this principle as a practical solution for once-through cooling application.
shows a conical screen designed 

### to handle 1.0 

### m3/s (16,000 gpm). 

### tions inwedge-wire screening are listed below: Wedge-wire screens alsoappear tobe 

### presently limited to relatively small flows. Figure 11 General engineering considera7.

2.



### 3. 4.


### 5.
6. 

### 7, Clogging. 

### toestablishsuitable hydraulic conditions for self-cleaning and the 

### removal of backflushed debris, therebyminimizing the clogging potential of the screen. An 

### adequate backwash system is

### alsorequired forperiodic cleaning of the screen. Compressed air

### or water can be utilized. In order to assess backflushing requirements at a specific siteand to determine the 

### potential forinterference 

### between adjacent screens (Fig. 72), 

### theoretical solutions, based on the potential flow theory, can be used. These solutions can determine the spacing and orientationof screens needed tominimize 

### the amount of backflushed debris from one screen that may accumulate on an adjacent screen which isina pumping mode. Parameters to be used inthe analysis include backflushing velocity, pumping velocity, ambient current velocityand directionand distance 

### between screens.(Colorado StateUniversity 1974). Velocity distribution. tominimize the probability of entrapment of motile organisms and tominimize the

### need for debris backflushing. 

### One approach 

### is tocarefully select the 

### screen length, screen diameter, and length of with

### drawal pipe penetration intothewedge-wire screen. screen shape, such as 

### the conical shape (Fig. 11) or a cylindrical shape with 

### an internal diffuser. Navigation. The screens

### must be 

### located such that they do not interfere with

### navigation. Large debris. screens ordamage them. Frazil ice. In northern latitudes, provisions forthe prevention of frazil ice formation on the screens

### must be considered. Biofoulin


## . Screen materials should be used 

### which will minimize 

### the degree of biofouling 

# + its

### effect on hydraulic efficiency. Access. The screens should be 

### readilyaccessible formaintenance and performance monitoring. The screens should be 

### located 

### inan ambient current of atleast 30 

### cm/s (1 

### fps)

A uniform velocity distribution along the screen face is 

### required Several approaches exist to achieve uniform velocity (Cook 1978)

# - Another approach is 

### to select a

In many areas, largedebris 

### (trees, etc.) and pack ice could block the

To date, proven methods for adequately cleaning the 

### screens by backflushing and preventing frazil iceformation have not been developed for once-through cooling systems that utilize a large number of wedge-wire screens. However, general engineering factorswhich should be 

### considered during the

### developmental efforts areas f

### 011 

### ows: 

### 1- Resistance of the structureto erosion under prevailing current and wave conditions. As stated, porous dikes have not yet been developed foronce-through intakes.121 

# i36" DIA. INTAKEPIPE

SOLIDPLATEEND I 

# rn

Fig. 11. 

### Conical Wedge-wire Screen (1 inch = 

### 2.54 

### cm)

a. U = 0.2FPS, a=ODEG 

### BACKFLUSHING VELOCITY = 

### 1.0FPS

I- 

### 10 ft. 

## * b. U = 0.2FPS, 

### a= 90DEG 

### -5FPS

Fig. 12. 

### Streamlines Showing Movement of 

### Backflushed Debris between Wedge-wire Screens .(l 

### ft= 0.305 m). 

### Courtesy of Colorado StateUniversity.122


### 2. 3. 

### 4. 5. 6. 7. 

### 8. 

### 9. 10. Structural stabilityof dike 

### and foundation. Hydraulic stabilityof the

### dike and foundation against internal erosion. The capacity tocarry the design flow under biofouling and clogging conditions. Minimal effect on prevailing sedimentation or littoral drift patterns. Non-interference with

### boat traffic. Provisions for access, maintenance, and 

### monitoring of performance. Provisions forbackwashing the dike forremoval of debris or the melting of frazil 

### ice. Economic availability of construction materials. Viable and economical construction methods. 

# -

CONCLUSION Because the 

### concept of physically preventing the passage of small organisms into power plant cooling water systems 

### is relativelynew, there

### exists an obvious need to expand research efforts inorder 

### to develop and refine the technology required 

### to achieve 

### this goal. be apparent that the biological requirements forprotecting small organisms create engineering problems which 

### have not been of concern in

### the past. developmental efforts be conducted with 

### close interactionbetween engineers and biologists. being evaluated for

### the protection of small aquatic organisms. protection systems have been highlighted such that they can be 

### maintained in

### future developmental efforts. direction tofurtherresearch. It

### should Therefore, it

### is imperative that future
This 

### paper has addressed many of 

### the problem areas which 

### existwith 

### the systems presently Positive features of specific Negative features have likewise been identified 

### inthe hope of supplying
Atthis 

### time, it 

### appears that impinging concepts offer 

### the most practicable solution to 

### larval entrainment problems atonce-through cooling sites while 

### deterrent concepts arelimited 

### toclosed-loop cooling systems. The-choiceof a larval protection system for a prototype application depends on biological effectiveness and on engineering and cost considerations.

REFERENCES 

### Alden Research Laboratories. 1974a. Hydraulic Model Study (Link-Belt 

### Dual Flow Screens) Report No. 

### 69-74/MlORF. Prepared for Long Island Circulating Water Pump 

### Structure. Lighting 

### Company and Stone & 

### Webster Engineering Corporation. Circulating Water Pump 

### Structure. ing Company and Stone & 

### Webster Engineering Corporation. Colorado StateUniversity. Gulf States Utilities Company. Cook, L. E. 

### 1978. The

### Johnson Screen for Cooling Water Intakes, pp. 

### 149-157. 

## &R. K. 

### Sharma and J. B. 

### Palmer (eds.), Larval Exclusion Systems for Power Plant Cooling Water Intakes, Proceedings of theWorkshop held atShelter Island Inn, San Diego, Calif., Feb. 

### 7-8, 1978. NUREG/CP-002. Argonne National Laboratory, Argonne, 111. 1977. ting 

### Fine-Mesh Traveling Screen to Reduce Ichthyoplankton Entrainment atIndian Point Generating Station. Hanson, B. N., W. H. 

### Bason, B. E. 

### Beitz, 

### and K. E. 

### Charles. 1978. Practicality of Profile-wire Screen in

### Reducing Entrainment and Impingement, pp. 

### 195-234. In R. K. 

### Sharma and 

### J. B. 

### Palmer (eds.), Larval Exclusion Systems for Power Plant CoolinrWater Intakes, Proceedings of theWorkshop held atShelter Island Inn, San Diego, Calif., Feb. 7-8, 1978. 002. Argonne National Laboratory, Argonne, 111. Alden Research Laboratories. 1974b. Hydraulic Model Study, Beloit-Passavant Traveling Screen, Report No. 70-74/MlORF. Prepared for Long Island Light1974. Hydraulic Model Study, 

### River Bend Station 

### - Units 

### 1 and 2, Prepared for Stone & 

### Webster Engineering Corporation.

Ecological Analysts, Inc. Preliminary Investigations Into the 

### Use of a Continuous OperaPrepared for Consolidated Edison Company of New 

### York, Inc.

NUREG/CP-123 Murray, L. S., and T. S. Jinnette. 1978. Survival of Dominant Estuarine Organisms Impinged 

### on Fine-Mesh Traveling Screens 

### atthe Barney M. Davis Power Station, pp. 79-87. In R. K. Sharma and J. 6. Palmer (eds.), Larval Exclusion Systems for Power PlantTooling Water Intakes, Proceedings of 

### the Workshop held at Shelter Island Inn, San Diego, Calif., Feb. 7-8, 1978. NUREGICP-002. Argonne National Laboratory, Argonne, Ill.
pp. 288-295. Texas A&M University, College Station, Texas, August 10-12, 1977. Mussalli, Y. G., and E. P. Taft. 1977. 

### Fish 

### Return Systems inHydraulics 

### inthe Coastal Zone, In Proceedings of 

### the 25th Annual Hydraulics Specialty Conference, ASCE, 

### Mussalli, 

### Y. G., E. P. Taft, and P. Hofmann. 1977. Engineering Implications of 

### New Fish Screening Concepts, pp. 367-376. In Proceedings of the Fourth National Workshop on Entrain

### ment and Impingement, Chicago, Illinois, December 5-7, 1977. Nikonorov, I. V., and M. B. Mel'nikova. 1974. Technical and Biological Fundamentals 

### of Fish Protection In Water Intake Structures, Rybnoe Khozyaistro, No. 2, February 1974, pp. 14-17. Translated by National Marine Fisheries Service, Office of International Fisheries, Language Services Division. Pavlov, D. S., and 

### A. M. Pakhorukov. 1973. Biological Basis of Protecting Fish From Entry Into Water Intake Structures. 

# IflPishchevaya Promyshlennost', 208 p. Translated by S. Pearson, National Marine 

### Fisheries Service, Northwest 

### Fisheries Center, May 1974. Saffran, E. P., and R. A. Kormanik. 1976. Designing Microscreens? 

### Here's Some Help. Water & Schuler, V. J., and L. E. Larson. 1975. Improved Fish Protection atIntake Systems, Proc. Am. Taft, E. P., P. Hofmann, P. J. 

### Eisele, and T. J. Horst. 1976. 

### An Experimental Approach to

### the Wastes Engineering, April.
SOC.Civ. Eng. Journal of EE6 101:897-910. Design of Systems For Alleviating Fish Impingement atExisting and Proposed 

### Power Plant Intake Structures, pp. 343-365. Workshop on Entrainment and Impingement. Taft, E. P., and Y. G. Mussalli. 1977. Biological and Engineering Investigation of Angled Flush Fish Diversion Screens, inHydraulics In the Coastal Zone. Proceedings of the25th Annual Hydraulics Division Specialty Conference. American Society of Civil Engineers, Texas A & M University, College Station, Texas, August 10-12, 1977, pp. 304-312. Taft, E. P., and 

### Y. G. Mussalli. 1978. Angled Screens and Louvers For Diverting 

### Fish atPower Plants. J. Hydraul. Div. Proc. 

### Am. SOC. Civ. Eng. 104:623-634. Tomljanovich, D. A., J. H. 

### Heuer, and C. W. Voigtlander. 1977. Investigations on the Protection of Fish Larvae atWater Intakes Using Fine-Mesh Screening. Tech. Note No. B22. 36 pp

## KL. D. 

### Jensen (ed.), Proceedings of the Third National

Tennessee Valley Authority Tornljanovich, D. 

### A., J. H. 

### Heuer, and C. W. Uoigtlander. 1978. Investigationson the Protection of Fish Larvae atWater Intakes Using Fine-Mesh Screening, pp- 125-139. In R. K. Sharma and J. B. Palmer (eds)., Larval Exlcusion Systems for Power Plant Cooling WaterIntakes, Proceedings 

### of the Workshop held atShelter Island Inn, San Diego, Calif., Feb. 7-8, 1978. NUREG/CP-002. Argonne National Laboratory, Argonne, 111.