ML17053D821
| ML17053D821 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 02/29/1976 |
| From: | Eisele P, Hofmann P, Taft E STONE & WEBSTER ENGINEERING CORP. |
| To: | |
| Shared Package | |
| ML17053D800 | List: |
| References | |
| NUDOCS 8306080351 | |
| Download: ML17053D821 (26) | |
Text
AN EXPERIMENTAL APPROACH TO THE DESIGN OF SYSTEMS FOR ALLEVIATINGFISH IMPINGEMENT AT EXISTING AND PROPOSED POWER PLANT INTAKE STRUCTURES By E.
P. Taft P.
Hofmann P. J. Eisele T. J. Horst Stone 4 Webster Presented at the Third National Workshop on Entrainment and Impingement; Section 316b - Research and Compliance Considerations New York City, February 1976 830608035i 830606 PDR ADOCK 050004i0 A
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An Experimental Approach to the Design of Systems for Alleviating Fish Impingement at Existing and Proposed Power Plant Intake Structures E. P. Taft, P. Hofmann, P.J. Eisele,and T. Horst Stone 8t Webster Engineering Corporation Boston, Massachusetts 02107 INTRODUCTION 344 Third National Workshop on Entrainment and Impingement Point Generating Station (Indian Point) and the proposed Cornwall Pumped Storage Project (Cornwall), both located on the Iludson River and owned by Consolidated Edison Company of New York, Inc (Con Edison).
Field studies have been designed to evaluate the effectiveness of a bottom sill in reducing the impingement of fish, mainly of the bottom.dwelling variety. A bottom sill has been installed at the Boston Edison Company (BECO) Mystic Station, unit 6 (hfystic-6), located on the Mystic River.
The following text is a description of the various devices and systems investi-gated in these studies, the experimental programs designed I'or evaluating the effectiveness of the systems, and a general discussion of the results obtained.
Impingement of fish in cooling water intakes can create both biologic and operational problems at power plants. There are basically two approaches to alleviating potential fish impingement at either existing or proposed power plants.
The first approach is to install a device that is known to alleviate impingement of fish at other water intakes. Unfortunately, because information on the applicability ofspecific devices under different physical and biologic con-ditions is generally lacking, it is often difficultto ensure that a particular device willbe effective for a speciTic site.
A second approach involves testing a device prior to installation. Because licensing requirements necessitate a certain degree of assurance that a system will bc effective, and cost commitments for installation of diversion devices may be substantial, it would appear to be prudent to evaluate the effectiveness of particular devices prior to installation. This approach could also avoid the cost ol'utages, redesign, and installation of a second intake system after the impact of the initial, untested system proves too great.
By utilizing this alternate
- approach, thc decision to install a particular device will be made with a reasonable degree of assurance that the device will be effective in alleviating impingement.
This paper will discuss various Iield and laboratory study programs that were designed to investigate the applicability of diversion devices for specific sites.
Stone & Wcbstcr Engineering Corporation (S&W) has been both conducting laboratory model studies and evaluating monitoring data on impingement for several utilities. The laboratory studies have been designed to investigate methods for alleviating potential fish entrapment at several existing and pro-posed Lake Ontario power plants owned by Niagara hfohawk Power Corporation (NhIPC) and Rochester Gas & Electric Corporation (RG&F) and at the Indian EXPERIMENTAL PROGRAM hlodel studies for NhIPC and RG&E have involved the development of methods for diverting and bypassing fish within onshore screenwells, preventing fish entrapment at oflahore, submerged intake structures, and safely returning fish from both locations back to Lake Ontario. Test species were selected on the basis of their abundance in screenwashing samples at existing intakes or their commercial and sport value.
TIte species tested were the alewife (Alosa pseudrrharcngtrsJ, smelt (Osrnenrs inordax/, and coho salmon (Oncorliyncltus kisurch/. Studies for NhIPC began in May l973 and were designed to evaluate the potential effectiveness of angled traveling louvers and screens for screenwcll guidance application, wide-spaced louvcrs for offshore intake application, and various pipe and pumping elements needed to transport fish from bypasses back to the lake. Initially,the intent of these studies was to develop design criteria for fish diversion devices that could be applied to Nine hlile Point Nuclear Station, unit r (NhIP.2). Early in 1975. the scope ot'he studies was expanded to include other intakes at power plants located on Lake Ontario and owned by NMPC and RG&E. The primary objectives ol'hese studies are to further evaluate the potential for general application ot'n angled traveling screen for fish diversion withitt existing and proposed serecntvell structures on the lake.
Because the existing Indian Point and proposed Cornwall generating facilities are designed witli onshore intakes. laboratory model studies for Con Edison, wliicli began in tttid-I974. aie designed to dcvclop lish diversion systems for sereenwell application only. On the basis ol'an extensive literature review and experience gained Iruin thc NMP( studies. angled traveling louvers and screens werc seleetcd I'or inodel testing.
Test species include white perch (h(orone arncrit anai. striped bass (h(rrruna sava(ilisf. and tomeod (hlicrogadtrs (untrodj.
Regulatory concern that the operation of additional units at hlystic Station would result in additional iinpingement of benthic species. particularly winter
Taft et al.: Alleviating Fish Impingement Third National Workshop on Entrainment and Impingement flounder (Pseudopleuronecres americartus/,
led to the development of a bottom sill for this station. A bottom sill has been installed at the Mystic Station, and a preliminary field evaluation has been conducted.
Studies conducted to develop screenwell fish diversion systems, offshore intake diversion systems, and associated transport systems are discussed indi-vidually below.
Screenwell Fish Diversion Systems Essentially the same approach was taken in developing screenwell fish diversion systems for NMPC, RG&E, and Con Edison. The basic experimental apparatus used was the test flume. Three flumes have been utilized for evalu-ating the effectiveness of angled traveling louvers and screens. Table I presents a
list of pertinent information relative to the engineering and biologic parameters evaluated in each flume.
The first flume constructed was 3 ft deep, 3 ft wide,and 70 ft long and was used to develop an acceptable louver design for application at NMP-2. Louvers were selected for evaluation on the basis of an extensive literature review.
Louver systems, which create a velocity gradient along which fish will guide, have been shown to be effective in diverting a variety of fish species on the West Coast to bypasses (Bates and Jewett 1961; Bates et al. 1960; California Depart-ment of Water Resources 1967; Downs and Meddock 1974; Ducharme 1972; IIallock et al. 1968; Ruggles and Ryan 1964; Schuler 1973; Thompson and Paulik 1967; United States Fish and Wildlife Service l960). Information obtained from past studies was utilized in establishing initial test parameters.
Variables investigated included louver array
- angle, louver slat
- spacing, approach and bypass velocity, species, temperature, and light conditions. A by-pass width of 6 in. was maintained throughout the study program. In all tests, the louver slats were set at a right angle to the louver frame. Each slat was 3 ft long, 3.5 in. wide, and 0.5 in. thick.
Forty-five tests with various louver arrangements were conducted between August 1973 and October 1974. Louver angles of 90, 60, and 25 to the flow and louver slat spacings of I, 2, and 3.25 in. were tested. The approach to bypass velocity ratio was always set at approximately 1.0:1.5. Therefore, at the three different test approach velocities of 1.0, 1.5, and 2.0 ft/sec, bypass veloci-ties were 1.5, 2.3, and 3.5 ft/sec, respectively.
Based on initial results of testing in this flumc, a louver array angled 25 to the flow was chosen for a more detailed analysis.
An analysis of the data collected indicated that the spacing between louver slats and the approach and bypass velocity were associated with the efficiency of the system in diverting fish. Water temperature also affected the efficiency. The average Cl E
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Taft et al.: Aileviating Fish Impingement Third National Workchopon Entrainment and tmpi efficiency of the louver system for all tests conducted at a louver array angle of 25 and a louver slat spacing of l in. was 90%%uc, with a standard aeviation of 7.3 (3l tests with 200 fish per test). A more detailed discussion of the test design, procedures, results, and conclusions of these tests may be found in a separate report (Stone &. Webster Engineering Corporation l 975).
Although results of louver testing indicated that such a system would function relatively eff'ectively in a power plant screenwell, developments in the design of angled traveling screens, similar to the conventional type, warranted an investigation into the feasibility of utilizing such a concept for guiding fish to a bypass. An angled traveling screen offers several advantages over a louver system for power plant application. Most important is the fact that because the screen acts as both a diversion device and a screening medium, backup screens, required behind louver systems for removal of fine debris and nondiverted fish, are not necessary.
Therefore, an engineering and biologic feasibility evaluation was con-ducted early in l 975, and, on the basis of information obtained, a test program was initiated to develop and optimize the effectiveness of an angled screen in diverting fish to a bypass.
Initial studies, conducted in the 3.ft flume previously described, showed that a screen, angled 25 to the flow and leading to a 6-in. bypass, diverted lSYkof the test fish (alewives and smelt) without impingement. Due to size limitations, however, it was not possible to incorporate all of the important design features of an angled traveling screen into the 3-ft flume. Therefore, a second flume was constructed to allow a more complete evaluation of the device. This flume was 6 ft wide, 6 ft deep, and 40 ft long (Figure l). A simulated traveling screen, structurally identical in every detail to a full.scale screen, was installed at a 25 angle to the approach flow. The screen leads to a 6.in. wide bypass with a sloping roof that directs the bypass flow into a 12-in. diameter pipe. This pipe then enters a collection area from which bypassed fish can be removed. Alter-nately, the pipe can be connected to a system of pipes and a jet pump, as described later, designed to evaluate a complete diversion, bypass, and return system for Lake Ontario application.
A similar flume, with an overall length of 80 ft, is being utilized to evaluate angled traveling louver and screen diversion devices for Con Edison (Figure 2).
The approach section of the flume is 6 ft wide and 7 ft deep.
Tests are conducted at a water depth of 6 ft. The louver and screen test devices are fabri ~
cated in sections and are interchangeable.
This system permits testing with both devices under similar water quality conditions and allows for simplified altera-tions to the angle
" f the device to the approach flow.
A 6-in. bye ss has been utilized in all tests. Water flows along the bypass at the full 6.ft depth to a baffle wall where the flow separates and passes around tlie wall before exiting through a screen.
Fish collect in a quiescent area behind the wall where velocities are low.
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sQ C0 no OO tr Because the test procedures and results of both the NMPC/RG&E and Con Edison flume studies were very similar, tliey are discussed together below.
Variables investigated include species, approach and bypass velocity, lighting condition (light or dark), water temperature (and various other water quality parameters),
length of test, test and control mortality, and differential mortality (Table I). Mortality is observed for 7 days after each test with the angled traveling screen devices. The purpose of these studies is to determine whether stress, such as contact with the screen or prolonged energy exertion, occurs as a result of testing, which may affect the survival of bypassed fish. The procedures utilized involve holding all test fish for I week and comparing mortality among these. individuals with that of a control group of fish. In most cases, fish have been tested only once; that is, test and control fish consisted ofindividuals that had not previously been exposed to a test device or to the handling involved in removing controls to a holding box.
During I.week mortality studies, all fish that die during each 24-hour period are weighed and measured to the nearest O.l g and 1.0 mm, respectively, for determination of condition factor, K. At the end of I week, a subsample of remaining live fish is sacrificed, weighed, and measured.
During louver studies for Con Edison, mortality studies are not conducted, because it is assumed that bypassed fish willnot suffer any higher mortality than fish diverted by a screen and that the loss of fish through the louver structure provides an adequate basis for efficiency evaluation. However, the coefficient of condition was determined for all fish that passed through the louver device, and for an equal number of bypassed fish, to determine whether condition is a factor in louver diversion efficiency.
To date, the louver and screen angle evaluated in both flumes has been 25 to the flow. Approach and bypass velocities with the angled screen have always been equal and have ranged from 0.5 to 3.0 ft/sec. In evaluating the louver device fur Con Edison, the approach to bypass velocity has always bccn set at a ratio ot 1.0:1.5. Therefore, at test approach velocities of 1.0, 2.0, and 3.0 ft/sec, bypass velocities have been approximately 1.5. 3.0, and 4.5 ft/sec, respectively.
In most cases, the angled screen was found to be IO(ye~effective in diverting all test species (alewife, white perch, tomcod, and striped bass) to the 6.in.
bypass under all test conditions occurring in both test flumes. In addition. I-week survival was considered to be an important criterion for deterinining the overall effectiveness of the device.
A least-squares analysis of covariance (ANCOVAI was pcrlormed on I.week inortality data with alewives (NMPC/
RG&I', i. Brrllt total and differential mortalities were analyzed with temperature, velocity. and incan coclticicnl of condition as independent variables. Velocity had a
signilicant effect o>> lotal mortality (p = 0.015): that is, mortalily increased with increased velocity.
Results ol'n ANCOVA for differential
Taft et al.: Alleviating Fish Impingement 351 352 Third National Workshop on Entrainment and lrnpi nt mortality indicate that temperature was significant (p = 0.08), with a slight nega-tive effect: that is, dil'ferential mortality increased with decreasing temperature.
The mean differential mortality and 95% confidence limits were 35.7 + 13.5%.
The analysis was somewhat diflicult to interpret due to high test mortality and variable control niortality, presumably n suiting from the handling of this fragile species under laboratory conditions.
As with the NMPC/RGEsE studies, angled screen diversion efficiencies with Hudson River species were almost always IOO%%uo (32 tests, 200 fish per test).
One. week differential mortality was low in all cases (mean
= 3.3
. 2.5%), regard-less of test velocities, species, temperature, or lightbig condition. An ANCOVA showed that temperature significantly influenced mortality of both test and contcol lish (p = 0.002). However, the relationship was opposite to that found with alewives; that is, as temperature decreased, mortality decreased.
Results of louver testing in the Con Edison flume to date show that the device. angled 25 to the flow, is from 50% to 99%efficient in diverting the three test species to a bypass under all temperature, velocity, salinity, and light-ing conditions evaluated.
A preliminary analysis of the data obtained from 21 tests shows an average efficiency of 84.6
+ 5.4%. A detailed analysis has not been conducted.
As previously mentioned, field studies were conducted at the MysticStation lo evaluate the effectiveness of a bottom sill in alleviating the impingement of winter flounder. A screenwash monitoring program was initiated in mid.1971 to determine the numbers of lish impinged at the existing station. The results of the program werc to serve as a basis For predicting potential losses of fish at a new unit. The existing station consisted of six units with six intake bays. The flow into each bay varied. Titc monitoring program consisted of collecting all fish that were washed into thc screenwash sluiceway over a 24-hour period, 2 days each week. Fish densities were corrected for varying flows by calculating the numbers of each species collected for each unit volume of flow.
Based on the results ol'he monitoring program through 1973, it was deter-mined that losses of winter llounder at the new unit could be higher than those from existing units. In an attenipt to alleviate existing and potential flounder losses at the station, the decision was made to install a bottom sill at Mystic.6 to establish the <<fl'ectiveness of a sill as a deterrent to flounder.
tn late 1973, a bottom sill, which consisted of an 8 ft high wall, was placed upstream of thc trash racks at unit 6. The fish monitoring program was contin.
ued by use of units 1-5 as the control, or unaltered. condition. The effectiveness of the bottom sill was evaluated by using the log ratio of the monthly densities of lloundec from units 1.5 to the nlonthly densities from unit 6. The prebottom sill ratios were then compared to postbottom sill ratios by a one-tailed t test.
Preliminary cesults mdicate that there was a significant (p = 0.01) reduction in flounder impingement of about 5¹ after the installation of the bottom sill.
As a result of this evaluation, a bottom sill will be incorporated into the intake forebay of unit 7. Monitoring studies will then continue to verify the effectiveness of the device in the new unit.
Offshore Intake Diversion System A scheme for bypassing fish at the NMP-2 submerged offshore intake and returning them to the lake was proposed by NMPC in January 1974. The concept was developed on the basis of screenwell louver studies previously discussed.
However, because close spacing between louvers would be impractical at an offshore intake due to the potential for clogging by debris and frazil ice, it was proposed that wider spacings, combined with higher velocities, might act to establish the hydraulic conditions necessary to guide fish away from the main water flow and into a bypass (Figure 3). Approximately 10% of the flowenter-ing the intake structure is drawn into the bypass.
A series of preliminary biologic tests was conducted with coho salmon in a scaled model of the concept.
Results were encouraging, and I:9-and I: I-scale intake segment models were constructed to more fullyevaluate the potential of this scheme.
Results of the I:9-scale hydraulic model were used to develop initial design criteria for the I:I-scale segment model. This model was constructed inside a basin approximately 60 ft wide, 70 ft long, and 6 ft deep (Figure 4). Six pumps, with a combined capacity of 130 ft /sec, were installed to circulate water through the model.
The test procedure involved placing fish in the model upstream ofthe intake structure and monitoring their passage through the system over time. The variables investigated included approach velocity, ratio of approach to bypass velocity, and water temperature.
The results of the offshore intake louver study were analyzed with an ANCOVA (41 tests, 500 fish per test). The efficiency of the system in diverting fish was increased by increasing the approach velocity and increasing the ratio of approach to bypass velocity. The range of approach velocities tested was between 1.5 and 4.0 ft/sec, while the ratios tested were 1.0-1.67. The efliciency of the louver system also depend on water temperature and the year in which the system was tested. The overall average efficiency for all tests with alewives was 49%, with a standard deviation of 21%.
Fish Transport System Both the offshore intake diversion system and the screenwell guidance system developed tor rfMPC require a tish transportation system to return fish safely to
Taft et al.: Alleviating Fish Impingement 353 Third National Workshop on Entrainment and Impingement vERTICAL SHAFT
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Lake Ontario. The transportation system that has been developed by S8IW involves the use of a jet pump to induce flow into a bypass and to drive the Aow in the pipes used to transport fish. A jet pump was selected for evaluation because it has no moving parts and is, therefore, easily maintained and has a low potential for injury to lish resulting from contact with pump compI ients.
Models were constructed to determine the effects of two different type. of jet pump and the effects of passage through a pipe at various velocities n fish viability. In addition, the effects of the various pressure changes that fish would experience ln passage through the entire intake system were determined by test-ing in a pressure chamber.
A des<<ription of these studies and the results that were obtained follow.
Figure 4. I:t~ie ratio offshore intake segment modek Jet Pump Studies A jet pump is a unit that performs its pumping action by the transfer of energy from a high-velocity jet to one of low velocity. Two types of jet pump were evaluated:
a core type, in which a concentric nozzle is placed centrally, and a peripheral type, in which the nozzle is placed around the periphery (Figure 5).
To utilize a jet pump to pass fish safely requires hydraulic design information on its performance characteristics and information on the effects of the hydraulic jet shearing forces on fish mortality.
The core-type jet pump model (Figure 6) consisted of a 2.tt diameter, 14-ft long mixing tube and an S.in. diameter driving nozzle, resulting in an area ratio
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wide, 55 ft long. and 6.5 ft deep. Biologic testing was conducted by introducing lish directly into tlie jet Aow via a 3.in. dialilclcf plastic pipe. On release, fisli were passed through the mixing zone and were discharged I'rom the 2-ft dianieler niixing tube hilo an I 8-by-22-ft collecting area.
Taft et al.i Alleviating Fish Impingement 357 358 Third National Workshop on Entrainment and Impingement The peripheral-type jet pump (Figure 7) was evaluated in a 4-in. diameter model with a 2.5.ft mixing tube. The model was installed in a 2-by-2-ft flume approximately 30 ft long. The biologic test procedure consisted of placing test individuals directly into the suction pipe. Jet nozzle velocities of30, 40, 50, and 60 ft/scc were evaluated.
With a core jet pump, test individuals displaced normal schooling behavior in all cases and showed no signs of damage or stress after passage through the pump (seven tests with a total of 360 fish). One-week mortalities of both test and control fish were low.
Similar results were noted with the peripheral jet pump (29 tests with a total of 1,244 fish). By observing fish after passage through the pump, and by comparing 1-week test and control mortalities, differential mortality was found to be low For all three test species (less than Ifyro) at a jet nozzle velocity of 30 ft/sec.
Because physical damage (scaling, loss of orientation) was more evident as jet nozzle velocity was increased to 40, 50, and 60 ft/sec, the poten-tial for mortality appeared to be higher at these higher test velocities. However, an analysis of the data showed no significant relationship between velocity and mortality duc to a limited number of tests and large variability in test and control mortalities.
Although the core jet pump proved to be a safe and effective means of trans-porting fish among the various components of the fish diversion system, the peripheral jct pump has been chosen for prototype application. The latter is deemed morc practical because it has a lower potential for damaging fish f Figure 8). The nozzle piping of a core jet presents an obstacle to approaching fisli that could cause a loss of orientation and physical damage due to abrasion.
Comparison of the prototype pump with the iuodel shows that this condition was not accounted for in the test procedure. Also. the nature of the core jet is such that fish entering thc mixing zone would be forced toward the sides of the mixing lube and could, tlierefore, bc further injured due to abrasion. The peri-pheral jct pump would present no obstacles to the fish and would tend to force them to the center of the mixing tube, thereby minimizing the possibility of abrasion of the sides.
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Taft et al.: Alleviating Fish Impingement 361 362 Third National Workshop on Entrainment and Impingement a holding tank for determination of I-week survival. An equal number ofcontrol lish was subjected to the same procedure, except for passage through the pipe, and then was placed in a separate tank for comparison ofmortality.
Tests were conducted at velocities up to 9.5 ft/sec. In every case, the test fish showed no visible signs of damage or stress when collected. The mean differ-ential I-week mortality and 95%confidence limits at all velocities tested were
-2.8 + 7.5 for alewives (eight tests with a total of 187 fish) and+7.6+ 11.9 for smelt (8 tests with a total of 645 fish). Higher mortalities in both test and control fish correspond to outbreaks of bacterial infection.
Results of these studies will be utilized to design pipe dimensions and veloci ~
lies in the prototype system. At this time, it appears that velocities up to 8 ft/
sec are safe for transporting fish.
Pressure Study Fish entering the NMP-2 submerged offshore intake willbe subjected to pres-sure changes during their passage to the screenwell. Fish that are bypassed in the screenwell will be exposed to further changes as they are transported back to lake Ontario. Very little informalion is available in the literature on the possible effects that these pressure changes may have on fish. Therefore, a test pressure chamber was constructed in which the pressures experienced by lish over time could be simulated.
Thc chamber was a square metal box, I It on each side. One-inch. thick Plexi ~
glas>n windows on the front and back of the chamber allowed observation of the fish during testing. Pressure was supplied by a compressor capable of produc.
ing 85 Ib/in.2 within the chamber. Two valves were used to regulate the pressure in the chamber over a given time.
for the purpose of this study, calculations werc made of the degree and time of exposure of lish to positive and negative pressures as they passed through the NMP-2 circulating water system, including the bypass and return facilities.
During testing, lish were placed in the pressure chamber and subjected to the positive and negative pressure changes that they would experience in the proto.
type intake. After testing, the fish were removed from the chamber and placed in a holding tank. One-week mortality was recorded and compared with that of control fish.
Prcssure chamber testing resulted in mean differential mortality values and 95'1. confidence limits of -20.83 4 21.1 for alewives (six tests with a total of 68 fish) and -11.3+ 16.0 for smelt (eight tests with a total of 160 lish). Iligh mortality was experienced in both lest and control fish at certain times due to a bacterial iilfcction. This finding wr>ulil indicate that the mortality was not attributable to pressure stress, but rather to natural stress that resulted from the fungal infection. Therefore, it appears that pressure changes in the prototype intake system would not adversely effect the condition of fish entering it.
Prototype System Demonstration To evaluate the cumulative effects of all of the components of a prototype screenwell fish diversion and return system for NMP-2, a large model was con-structed that consisted of an angled
- screen, bypass, piping, jet pump, and coUection area (Figure 10). The model was also used to verify the system's hydraulic characteristics, which had been calculated through a computer analysis under a wide variety ofoperating conditions.
The angled screen and model basins previously utilized for NMPC/RG8sE flume testing were incorporated into the system demonstration model. At the end of the sloping angled screen bypass, a 10-in. inside diameter polyvinyl chlo-ride pipe was fitted to the 12-in. diameter pipe previously described. This pipe, which contained six horizontal and vertical 90 bends, then carried the bypass flow to a jet pump that acted as the driving force. Two pumps supplied the driving flow to the jet pump. Exiting from the jet pump, a mixing tube carried the flow to a secondary lish bypass area that contained an angled screen.
Fish entering the secondary bypass guided along the screen into a holding area from which they could be removed in a netted box without further handling.
As previously discussed, testing of the angled screen device for NMPC/RGEcE resulted in a mean differential Sday mortality and 95% confidence limits of 35.7 + 13.5%. Results of system demonstration testing indicate that these values may be conservatively high.
It would be expected that mortality in the system demonstration would be higher than mortality with the angled screen alone due to cumulative stresses that result from passage through a pipe and jet pump at high velocities and guidance along a second screen to a collection area.
However, this expected higher mortality was not observed.
In three tests (500 fish per test) with screen approach and bypass velocities that ranged from 1.0 to 2.0 ft/sec, pipe velocities from 5 to 9 ft/sec, and jet nozzle velocities from 30 to 50 ft/sec, the mean difl'erential mortality and 95% confidence limits in the system were 7.6+ 9.8%.
T)te results of a simple t test of the mean mortalities of angled screen and system demonstration tests indicate that the differential mortality was significantly lower Ia = 0.05) in the system demonstration than in tests with the angled screen alone.
Taft et al.: Alleviating Fish Impingement 363 Third National Workshop on Entrarnment and Impingement F ISH COLLECTION FACILITY
~ ANGLED SCREEN FLOW dcinonstration tests may be more indicative of the latent mortality that might occur in such a system constructed on Lake Ontario.
~
CONCLUSIONS MIXING TUBE XT PVMP SUCTION TUBE HEAD TANKg 0
ooo L PVMPS
~ VENTURI METERS INFLOW SCREEN TEST FLUME ANGLED SCREEN DRIVING FLOW PUMPS eYPASS-SUMP FLOW In instances where operating experience indicates a high potential for fish impingement, the use of hydraulic models and/or valuation in the field ol'arious techniques to minimize impingement can provide valuable design criteria for water intakes. This experimental approach provides two major advantages.
First. the information obtained by observing the reaction of fish under various simulated design conditions allows for an evaluation of potential effectiveness over a wide range of design criteria. Models can be constructed so that design changes can be readily accommodated in a short period of time, whereas changes to an actual intake without some assurance of effectiveness would be time con-suming and expensive. The second major advantage of these types of studies is that the information obtained can serve as evidence, to various regulatory
- agencies, that the proposed facility intake represents a reasonable design for the protection of species that are indigenous to the area.
The studies described in this paper are ongoing, and the results given are, therefore.
preliminary. A dclailed description of results will be published on completion of the various study programs.
f rSH TRANSPORT ~X PIPE ACKNOWLEDGMENTS ELBOW METER trigure 10. NhtP unit-2 system demonstration model.
A possible explanation for this observed difference in mortality is that addi-tional handling of lest fish. as rcquircd for their removal from thc angled screen hypass collection area, resulted in greater stress and. thcrcfore, mortality in lhcsc tish. whcrcas fish tcs!ed in the system demonstcalion model were not handled suhsciiucntiy 'o their introduction 'o the test flume. Therefore, because il appears lhai liigh mortalities in tests with the angled screen alone are partially a cesull of fish handliiig as part of the test procedure, the results of the system We expr<<ss our appreciation to Messrs. J.L Hilke and J.M. Toennies of Niagara Mohawk Power Corporation, Mr. R.W. Gilkinson of Rochester Gas and Llectric Corporation, Messrs. L.A. Rodriguez and LR. Tuttle of Consolidated Edison Company of Ncw York, and Mr. F. Gottlich of Boston Edison Company for their technical assistance in conducting these studies and for their critical review of the manuscript.
We also thank Messrs. G.E. flecker, J. Larsen, and J.W. Leavitt of the Alden Research Laboratories for their input into the design, constcuclion, and operation of the various biologic and hydraulic mtsdeb and their aid in the interpretation of hydraulic data.
ln addition.
wc gratefully acknowledge Messrs.
Y.G. Musaalh and J.M.
Polcfka of Stone Ec Webstec Engineering (Licprscatitsn (or their dtrection ln the engineering aspects of the study program.
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