# Research

# Report

TRIALS OF 

## AN ACOUSTIC FISH DETERRENTSYSTEM AT HARTLEPOOL POWER STATION

A 

### W H

### Tumpenny,

### J M Fleming, 

### K P 

### Thatcher & 

### R Wood FawleyAquatic 

### ResearchLaboratoriesLtd



### Forthe 

### attention of: 

## Mr C J 

### L Taylor, 

### NuclearElectric

### plc, Barnwood
July 1995 FRRl631951

### INTRODUCTION

2METHODS 3


### 2.1 

### THESTUDYSITE 2.2 

### THE SOUND

### SYSTEM 2.3POSITIONING OF THE SOUND PROJECTORS 

### 2.4 INSTALLATIONOFTEF, SOUNDSYSTEM 

### 2.5 EXPERIMENTAL DESIGN 2.6 FISH

### SAMPLXNGAND ANALYSIS 

### 2.7 OPERATIONALCONDITIONS 2.8 STATISTICAL 

### ANALYSIS
3RESULTS 6


### 3.1 SPECIES COMPOSITION OF THE CATCH 

### 3.2 COMPARISONOF

### NUMBERS CAUGHTIN

### TESTAND 

### CONTROLPERIODS 3.3LENGTH DISTRlBaroNOF THE

### CATCH 3.4 CATCH WEIGHT
4 DISCUSSION
4.1 SPECIJtS

### DIFFERENCES 4.2 DAYNIGHT DIFFERENCES 

### 4.3 SIZE

# - RELATED

### DIFFERENCES 4.4 SCOPEFORxMPROVEMENTAT HARTLEPOOL 

### 4.5 IMPACT ONTBE

### LOCALSEALCOLONY

5 

### CONCLUSIONS

REFERENCES

APPENDIX 1 8
9 10 10 10 

### 11

12

1

FAWFEY aquatic research laboratories Ltd

## SUMMARY
Trials were carried out at Hartlepool nuclear power station, on the Tees Estuary, to determine the efficiency of an acoustic fish deterrent system as a means of reducing the impingementrates of fish on the coolingwater (Cw) intake screens. The ingress of clupeid (herring-family) fish, chiefly sprat 

### (Spraffusspraffus) and herring 

### (Clupea 

### harengus) at Hartlepool has 

### in the past reached levels which have proved operationally difficult to handle, as 

### well as environmentallyundesirable; at other nuclear sites 

### in the 

## UK, they have also led to intermittent 

### loss of generation. The principle of using acoustic deterrence for marine and estuarine fish 

### was previouslytested for Nuclear Electric plc in laboratorytrials, and field trials were performed 

### in 1993-4 at Hinkley Point nudear station. These previous trials, 

### in which an American sound generating system was employed, were considered to have been compromised by unsatisfactory performance of the equipment, although some reaction

### of the 

### fish was shown to occur. For the Hartlepool trials equipment of 

### UK manufacture, designed specifically for fish deterrence purposes, was used. A sound system comprising a programmeable signal generator, power amplifiers and an array of underwater sound projectors was installed at the CW intake. An acoustic modelling exercise was first undertaken to determine the optimum sound projector positions 

### in order to minimise unwanted effects caused by reflecting surfaces and sound source interactions. This led initially to an eight-soundprojector design, with 

### six of the units deployed along the intake wall and 

### two further units located in the middle of the dredged intake channel. following measurementof 

### the sound field around the intake, it was recognised that signals from the sound projectors close to the intake were being drowned out by 

### CW pump-generated noise 

### in the critical 

### 50-600 

### Hz range. Consequently, it was decided to add four more units to the mid-channel position to increasethe signal-to-noise ratio. Installation of the initial system took place 

### in late February, 

### 1995 and testing began 

### on March lst, based on a comparison of CW screen-catches for alternating sound-on and sound-off days. The revised sound projector configuration commenced operation on 

### 25th March andwas continued until 

### 12April. An estimated total of 

### I 1 1,630 fish were collected during the trials, comprising 48 species. The bulk of these were sprat 

### (43.6%) and herring 

### (41.2%), whiting 

### (7.7%) being the only other fish caught 

### in signicant quantities. The remaining species contibuted only 

### 7.5% by number. The initial performance of the acoustic deterrent system was generally poor, owing to the 

### low signal-to-noise ratio achieved, although herring catches were reduced significantly (pC0.05) under this configuration, by 

### 56.2%. The addition of further mid-channel sound projectors, however, brought an immediate improvement 

### in effect 

### for almost all species. The following figures indicate the percentage reductions measured for the main species groupings under 

### the final sound projector arrangement, along with the probabilities that these were significantly different from zero: All species combined 

# - 55.9% (px0.05) Sprat 

# - 60.1% (p<0.05) Herring 

# - 79.6% 

### (p4I.01) Whiting 

# - 53.5% (p<0.05) OtherAmbladder species 

# - 54.7% (p<0.05)
FAWLEY aquatic research laboratories LtdNon-swimbladderspecies 

# - 15.6% (ns). 

### In weight terns, the system reduced the catch of the top three species (sprat, herring and whiting) by 69.0%; for sprat and herringonly, the reduction

### inweight was 

### 73.3%. A few minor problems of overheatingwere experiencedwith the sound system over the first days of the Gal but these were quickly overcome. 

### A more important problem was discovered only at the end of the trial when the equipment was withdrawn, when it was found that 

### the sound projectors had become depressurised

### as a result of air 

### loss along the signal cables. 

### This led to an estimated reduction 

### in signal source level by 

### 6-8 

### dB over the duration of the trials, and this was correlated 

### with a progressive reduction 

### in deterrence efficiency. The results over the earlier phases with each sound projector arrangement suggest that the system’s efficiency could be improved by a further IO-20% now that 

### this problem has been eliminated. Further scope for improvement by rearrangement of the sound projector positions 

### is identified. The potential for application of acoustic deterrent systems to marine and estuarine power station 

### CW system appears to be equally as promising as for freshwater locations, where efficienciesof 

### 60-100% are now being reported, in Britain, similar systems are being used, for example

### by the National RiversAuthority (NRA) to protectfish at a river pumpingstation intake, by the power industry, and by fishery scientists for fish trapping and census purposes. The 

### NRA is also engaged 

### in more comprehensive testing with a view to new applications on hydroelectric and fish farm sites. 

### in the 

### USA, acoustic deterrent systems are also being appliedto inland powerstations andto exclude fish from irrigationschemes. 

### A local issue at Hartlepool was the presence of a seal colony within the adjacent Seal Sands nature reserve. English Nature and allied conservationistswere concerned that the sound signals 

### from the acoustic system might disturb seals which, prior to the trials, had bred successfullyfor the first time in manyyears. An independentsurvey 

### of the 

### sealswas undertaken 

### in parallel 

### with the fish monitoring survey, by a team of seal specialists. The seal survey concluded that the seals showed no signs of distress or harm during the trials and that, from the point of view of the seals’ welfare, there should be no problem with the permanent installation of an acoustic deterrent system at the power station. Since the survey was completed, a pup has been bornto this, somewhatfragile, colony.

Date.

# ..~J..:..X 

# .?.C
for FAWLEY aquatic research laboratories Ltd Marine and FreshwaterBiology 

### Unit Fawley, Southampton

### SO45 

### lTW, 

### UK.

FAWLEY aquatic research laboratories ttd

## I 

## INTRODUCTION

Much research has been devoted to alleviatingthe problem of fish impingement at the cooling water (CW) intakes of power stations, both to avoid the disposal and operational problems caused by screen blockage, and to reduce the ecological impact (Turnpenny and Coughian, 1992; Langford, 1993). Solutions attempted range from the use of behavioural deterrents (based on light 

### or sound), to mechanical handling systems wherebythe fish are returnedto the water, dead 

### or alive. Some of these have been partially successful. 

### For example a mechanical fish return system tested at Nuclear Electric's Sizewell 

### 'B' nuclear power stationwas capable of returning liveto the sea a large proportion (-80%) of the more robust shoreline species but not the more delicate pelagic species (Seaby, 1994). 

### A bubble curtain placed across the intakes of Nuclear Electric's Heysham 

### 2 power station reduced the catch of fish, predominantly the delicate clupeid species, sprat 

### (Spmftus

### spraffus) and herring 

### (Clupeus

### harengus), by nearly 40% (Turnpenny, 1993). The clupeid species form the majority of the fish numbers entrained at most British coastal power stations and occasionally are entrained 

### in numbers sufficientto force a reduction

### or shutdown of generation. While early work on the use of sound 

### for fish guidance, for example at 

### CEGB power stations 

### in the 1970~~ produced few good results (Turnpenny, 1988), more recent research has led to a better understandingof signal characteristics which are effective at repelling fish. This, combined with much improved hardware 

### for delivering the undetwater sound signal, has made the use of acoustic fish deterrents a practical proposition for reducing fish entrainment at water intakes. Initial trials of a simple underwater sound system at Oldbury-upon-Sevem nuclear power station (Nuclear Electric plc)yielded a 39% reduction in bass 

### (Dicenfarchus labmx) impingement on the 

### CW screens (Thatcher and Irving, 1992) and other trials at a river pumping station 

### in York showed that coarse fish catches could be reduced by 80% (Wood 

### ef a/., 1994). Researchersinthe United States (Loeffelman 

### et al., 1991a, 1991b; Klinect

### ef ai., 1992) have 

### shown that acousticfish deterrent systems can create diversion efficiencies of up to 100% undersuitable conditions. Following the initial success 

### of acoustic deterrents at Oldbury-upon-Sevem, Nuclear Electric plc, 

### in collaborationwith the EnergyTechnology Support Unit (ETSU, Hatwell), decided to support further development of acoustic signals suitable for repelling a broadspectrum of marine and estuarinefish, for potential applicationat tidal power and nudear generating sites. The study (Turnpenny et 

### a/., 1993) resulted in the development of a number of signals which were shown to be effective under laboratory conditions. The most promising signal found was a swept, low frequency signal 

### (400 Hz), which was shown to be effective against a vari0ty of marine and estuarine fish. An important feature was that fish did not become habituated to the signal over a trial period 

### of 1-2 days. Highly significant (p<O.OOI) repulsion from the sound source was achieved 

### with all species tested, 

### with the exception of eel (Anguilla 

### anguillaa). A field testing programmewas then established at Nuclear Electric plc's Hinkley Point 

### power station 

### in Somerset to try out this signal as a means of reducing fish impingement(Turnpenny ef a/, 1994). The site was selected chiefly because itwas also relevant 

### to ETSU's Tidal Power programme, being close to the potential Severn
FAWLEY aquatic research laboratories LtdBarrage line. A sound system was supplied by a specialist underwater acoustics company 

### in the USA (Argotec Inc., Florida), and a series of 42 days of testing (approximatingto 1 day on, 

### I day off, in succession) was carried out, the fish screencatch being compared for the sound-on and sound-off days. Unfortunately, the equipmentfailed to performto the requiredstandard, owing mainlyto problems caused by the extreme tidal range and velocities at HinWey, which overwhelmed the internal pressure compensation capabilities 

### of the submerged sound projector units. This resulted 

### in the system being operated at sound pressure levels below target values. The main finding from the trial was that fish numbers increased rather than decreased when the sound system was 

### inoperation. This was suggested to be caused by a diving reflexwhich occurs when the fish are exposedto high sound pressure levels: the effect of this behaviour being to bring the fish closer to the seabed level of the CW intake. Although this response was inappropriate, the important finding was that the fish did react to the sound. It was concluded by the authors that, by generating an effective levelfurther away from the intake, either by increasingthe signal level or by movingthe sound sources further upstream 

### in the flow, it would be possible to deter the fish. This conclusion was based upon the widely reported behavioural reaction of fish to sound, whereby the initial reflexdive is followed by horizontal dispersion away from the sound source (Turnpenny 

### ef a].,1994). Nuclear Electric considered that further testing 

### in 1995 would be worthwhile, and selected Hartlepool nuclear power station (Cleveland) as the test site. The site has an onshore intake and therefore offers easy access to the intake area; also, it has suffered a history of operational problems with spratlherring ingress, particularly during the summer months. Previous monitoring by the National Rivers Authority (Peaty,. 1993) indicatedthat, during the latewinter period, the fish numberswould be sufficiently high for statistically-validtrials but not so high as to make enumeration impracticable. A potential impediment to the deployment of an underwater acoustic system at Hartlepoolwas the proximity of the power station CW intakes to the Seal Sands SSSI (Site 

### of Special Scientific Interest), an area within 

### which the acoustic equipment was to be installed. 

### In order to obtain a permit to deploy and operate the equipment, Nuclear Electric engaged 

### in talks with English Nature and the local INCA (Industry Nature Conservation Association) group. The primary concern was that a population of grey seals (Halichoenrsgrypus) had successfully bred within the SSSI for the first time in many years and it was feared that the undewater sounds might disturb them. An acoustic modelling exercise was commissioned to determine the likely extent of the sound field (Petrie, Nedwell and Needham, 1995), from which it was considered unlikely by 

### INCA'S adviser, Or Susan Wilson, that seals would be disturbed by the proposed sound system. Nevertheless,a numberof steps were agreed to minimise the 

### riskto seals, viz: (i) boat access to the nature reservewould be restrictedto a period 

## e h from high water (HW) to minimisethe disturbance during the seals' hauling-out periods; 

### (ii) the sound system would be brought up to its operational level gradually over a number of days, increasing the level by no more than 10 dB per day from ambient noise levels 

### in the Seaton Channel; (iii) a seal monitoring programme would be put into effect by 

### INCA throughout the trial: itwas agreedthat if any adverse effect on the seals was detected, the trial would be suspended immediately.

FAWLEY aquatic research laboratories Ltd 2Itwas also recognisedthat the monitoring programmewould provide useful information on possible reactions of seals to acoustic deterrent sounds.


## 2 

## METHODS


## 2-1

## The Study Site Hartlepool power station is located on the north side of the Tees Estuary 

### in Cleveland, on the north-east coast of England (Figure 1). The CW intakes draw water from the Seaton Channel, which lies within the Seal Sands 

### SSSI. The intake is 

### of the onshore type, opening onto a 

### short, dredgedchannel, some 70 m 

### in length (Figure 2 ). FourCW pumps of nominal discharge 8.5 m3s-’ each have paired openings along a concrete sea wall, which forms the boundary of the power station. Normally, no more than three CW pumps are operated simultaneously. Water entering the CW intakes is filtered by drum screens fitted with 

### 10 mm square stainless steel mesh. Very small fish can pass through this (see Turnpenny, 1982 for mesh selection curves); for most species of sprat/herring shape, the critical size for penetration is between 

### 40 and 50 mm standard length. Any debris, including fish and other marine organisms, caught 

### on the screens 

### is backwashed bywater jets, conveyed along concrete gullies to trash collection pits, whence the amounts collected can be quantified. 

### 2.2 

## The Sound 

## System The sound system comprised three main elements, as shown 

### in the block diagram of Figure 3. Ail equipment was supplied by Fish Guidance Systems Ltd, of Southampton, 

## UK. The first element of the system 

### was the signal generator, FGS Model 1-08. This is a solid-state device which holds a pre-recorded signal on EPROM (ErasableProgrammable Read-only Memory). The unit has the capability 

### of storing up to eight selectable sound signals, although only one signal was installedfor the Hartlepooltrials (Empirical Series 

### No. 7 

### : see Figure3). The second element was the 

### FGS Model 400 power amplifier/ monitor, and the third element the Model 30/600 sound projector. The latter is an electromagnetictransducer, effectively an underwater loudspeaker. Each amplifier supported and monitored 

### two sound projector units. The Model 301600 sound projectors have a nominal sound pressureoutput of 174 dB re 

### 1 VPa @ 

### 1 

### in inthe frequencyrange 

### 10

# - 600 

### Hz. Pressure changes within the sound projector units caused by tidal depth changes had to be compensated; the lack of adequate depth compensation was one of the major reasons for the equipment difficulties experienced 

### in the 1993-4 Hinkley Point trials (Turnpenny et a/., 1994). Compensation within the Model 30/600 units is provided by compressible bladders; those fitted were able to accommodate a threefold increase over atmosphericpressure, e.g. a depth changefrom zero to 20 m. A fault with the sound system was detected, but 

### not until the end of 

### the triais when the sound projectorswere withdrawn. The type of signal cable used, which proved not to be air-blocked, led to the gradual 

### loss of compensation air via the signal cable cores. Although the sound projectors continuedto function throughout the trial, the 

### loss of air

FAWLEY aquatic research laboratories Ltd 3caused a gradual deterioration of signal strength; it is estimated that the source levels fell by 6-8 dB overthe duration of the trials. 

## 2.3 Positioning 

## of the Sound Projectors The basic aim of the acoustic deterrent system was to create a repellant acoustic field within the confines 

### of the dredged channel to minimise the number of fish entering the CW intake. The criterion for using the Empirical Series No. 

### 7 signal defined by Turnpenny et aL(l993) was that the sound pressure level (SPL) should be set at -30 dB above backgroundambient levels for effective repulsion. No initial backround SPL measurementswere available, and a value of 305 dB, as measured around the Hinkley CW intake (Turnpenny et a/, 1994) was assumed: given the more sheltered conditions at Hartlepool, this was expected to be an overestimate. An arrangement of sound sources was therefore sought which would yield SPLs 

### in the order of 135 dB re I VPa in the lowerwater velocity region 20-30 m ahead of the water intakes; this was to allow fish to pass along the shoreline without becoming entrained. 

### Also, since the mud flats adjacent to the intake channel can become exposed at lowwater 

### (LW), forcing all the water to enter via the confines of the channel and so creating high velocities, it was considered desirable to place additional sound sources further out into channel to dissuade fish from entering the channel area at LW. An acoustic modelling study was undertaken by Subacoustech Ltd using the PRISM acoustic model to determine the optimum placement of the sound projectors. The initial configuration used is shown in Figure 2. Direct measurements of the sound field were also made by Subacoustech once the systemwas operating (Petrie, Nedwefl and Needham, 1995). From initial measurements it became apparentthat the signal-to-noise ratio close to the intakes of the power station was well below that required, owing to high SPLs emanating from the CW pumps. These generated an acoustic signature with peak levels at around 50 and 250 Hz which masked the deterrent sound signal within the critical area infront of the intakes. After further PRISM modelling had been carried out, a decision was made to reinforce the mid-channel sound projector group with the addition of four more units, positioned in two groups of two, as shown in Figure2. 

### 2.4 

## Installation of the Sound System The Model 30/600 sound projectors were mounted 

### in welded steel frames for deployment. Those fitted along the intake wall were attachedto a chain bridle and lowered manually into position to abut against the concrete wall between the paired intake openings, 

### so as to sit betweenthe coarse screens. The mid-channel speakers were mounted two-to-a-frame and lowered by boat to the seabed at the required position. A chain and buoy attached to each frame marked the position and allowedfor subsequent retrieval. The cables from each were attached to 6 mm mild steel chain, using plastic cable ties, and brought ashore close to the intake structure. The chainswere attachedto a concrete mountingat that point The cables from all units were routed into the CW pumphouse, where the cabinet housing the amplifiers and signal generator was located. Power was supplied from a 240V AC, single-phase, 30A circuit.

FAWLEY aquatic research laboratories Ltd 4

## 2.5 

## Experimental Design The experimentaldesign used a systematic test patternwith alternating control (sound system off) and test (sound-on) days. Impingement rates of fish at coastal power stations tend to be highly variable both within and between days. Short-termvariations occur diurnally and with tidal changes; longer term changes are related to spring-neap cycles, water temperature, wind conditions and the seasonality of different species (Tumpenny, 1983). An effective test sampling programme must accommodate these sources of fluctuation. Past experience (e.g. Thatcher and Irving, 1992; Tumpenny et a/., 1994) has shown that a 24hour sampling unit is the minimum practicable, owing to tidal and diel influences. In some cases, where the potential residence time of fish between the point of deflection and the point of sampling is high, longer periods are required. At Hartlepool, this was not the case, as the CW inlets open directly into the screenwells; also, chlorine, 

### which 

### is toxic to fish, was being applied continuously at the CW intakes to effect biofouling control. This ensured that any fish entering the system were quickly disabled by the chlorine and removed from the screenwell by the drum screens, limitingthe possibility of carry-overof fish from control and test periods. The length of the trial was initially planned to be 30 days (15 control, 15 experimental). This was based on an indication of the variability of daily catches provided by the reported NRA sampling programme. 

### In practice, the trial had to be extended to 44 days, to give sufficient data after the sound projector configuration had been altered partway through the programme (see Section 3.2). 

### 2.6 

## Fish Sampling and Analysis Fish from all the working screens were collected using a net ( 10 mm stretched mesh) placed in the trash pit, over the end of the trash backwash gulley. This was emptied twice daily: once at 0900 h (night-time sample) and again at 1700 h (daytime sample). Whenthe samplesobtainedwere too largeto handle, subsamplingwas carried out; the smallest subsamplewas one-fourteenth. The fish were sorted, identified to species and counted. Individualswere measured 

### in length (standard length, to the nearest 5 mm). Separate recordswere kept of daytime and night-time catches. Samples of fish were weighed by electronic balance to 

### 0.1 g to allow catch biomass estimatesto be made. 

### 2.7 

## Operational Conditions Some deviationfrom the alternate control-experimentalpattern occurred during the first week of the experiment, owing to initial commissioning difficulties. The sound system was started up on 25* February, 1995 and broughtto full operational level b 

### ld March. The regular day-on, day-off pattern ran consistently from 

## dh March to 12 ti! April. Any deviation from the sound system's complete operation was noted (for example there were occasional overheating problems on the amplifiers during the initial period, until improvedventilation andthermal overload protectionwere provided). A record was kept of the number of CW pumps operating on each day of the survey. Normally, three pumps were operating. On days when only two pumps were working, fish catchvalues were multiplied by 312 to standardisethe data.

~ FAWLEY aquatic research laboratories Ltd 5

### 2.8 

## Statistical Analysis To compare the sound-on versus sound-off screen catches, the population geometric mean (PGm) catch per night or day period was calculated, following the convention for screen catch analysis established by Turnpenny et

### al. (1983):


### PGm=geometric mean(evatfancd(2dn-lJ 

## 1 Significance testing was carried out using a Student‘s t-procedure to calculate the least significant difference (LSD) between sound-on and sound-off conditions for 

### p<0.05, as described by Turnpenny and Henderson 

### (1992): LSD

## = to.os [n]4((l/n)(var1+ vat2)), where varl isthe variance of the catchwith sound-on, vat2 is the variancewith soundoff, these values being determined separately for each species and for each of the two sound projector arrangements. LSDvalues were computed as percentage reductions as follows: LSD% =loo* LSD/meanZ, where mean2 is the mean catch for the trial period with sound-off. A measured percentage reduction was then considered to be significant if it was greater than the computed LSD%for that species and trial period. Plotsof the cumulative percentage reduction 

### in catchwere calculatedas:

Comparisons of catch species composition and size composition for the experimental and control periodswere made using the 

## x2 statistic(Campbell, 

### 1974). Size distributions were compared using a modified t-test designed to cope with large sample sizes (the Ztest).



## 3 RESULTS
3.1 

## Species Compositionof the Catch During the 42 days of the survey, an estimated total of 

### 11 1,630 fish was captured in the screen samples, comprising48 recorded species. These are listed 

### in Table I, along with total numbers captured. Sprat and herring formed the dominant elements 

### of the catch, being 

### 43.6% and 

### 41.2% by number respectively. Whiting was the next most numerous species 

### (7.7%), whilst the combined numbers of all other species amounted to only 

### 7.5%. 

### A comparisonof the species composition 

### of the catch

### with respect

### to the sound-on and sound-off periods is shown 

### in Figure 4. Compositionvaried significantly 

## (x2= 14.1, p 0.01), caused chiefly by a disproportionately large reduction 

### in herring catch during ‘sound-on’ periods. In the remaining analysis, the data have been grouped into six categories: ‘Total Fish’ consisting of all the species combined; ‘Sprat‘, ‘Herring’, ‘Whiting’, ‘Other Fish with Swimbladders’ (excluding lesser sandeel) and finally, ‘Other Fish without Swimbladders’. lesser sandeels were excluded from the’ ‘Other Fish with
FAWLEY aquatic research laboratories Ltd 6Swimbladders’ category as the numbers were due entirely to a large ingress of 0-group individualson a single day during the trials (March 

### 17*), which would have distortedthe statistics. The distinction betweenfish with and without swimbladders was made 

### in the ‘Other 

### Fish’ categories, as those species possessing a swimbladder are generally more sensitive to sound pressure (see Blaxter, 1981; Hawkins, 

### 1986). A daily breakdown of the catch in each of these groups is given 

### inAppendix 1. 

## 3.2 

## Comparison of Numbers 

## Caughtin Test

## and Control Periods The data set was split into 

### two sections. The first was based 

### on the initial sound projectorconfiguration (‘Arrangement 

### 1’), when eight unitswere deployed, and goes up to March 

### 24fi. The second relates to the final siting which was designed to overcome the high background noise levels found close to the intakes, and used twelve sound projectors (‘Arrangement 

### 2’); this arrangement was in place for the period March 

### 25* untilApril 

### 12*. Table 2 gives the number of 

### fish caught 

### in each of the six categories for both testing periods, and compares hourly PGm ‘sound-on’ versus ‘sound-off’ counts. The data derived from the final sound projector arrangement demonstrate the best system performance and showed an overall 55.9% decrease in fish catch. Decreases were seen 

### in all of the remaining six categories: sprat 

### (60.1%), herring 

### (79.6%), whiting (53.5%), ‘Other Fish with Swimbladders (excluding lesser sandeel)’ (54.7%) and ‘Other Fish without Swimbladders’ (15.6%). Figures are also given 

### in Table 2 for percentage reductions in day and night periods separately, along with the t-test probability levels that the valueswere significantlydifferentfrom zero. The detailedvariations in catch reduction for day versus night are seen most clearly 

### in plots of cumulative proportionate reduction 

### in fish catch for sound projector Arrangements 

### 1 & 2 

### in Figure 5. The statisticalsignificance of these values is indicated bythe shaded areas of the graphs: where the plottedfigures overlap the shaded areas, it indicates that the percentage reduction is significantly different from zero at the p4.05 probability level. It 

### is seen that for most specieslgroupings, owing to high dayto-day catch variability at Hartlepool, a statistically-significant result was reached only towards the end of the period of testing. The following more detailed observations may be made: (i) 

### All 

### Species Combined: The data for Arrangement 1 indicate that there was a modest reduction 

### in catch in both the night and day sampling periods when the sound projectorswere 

### in operation 

### (29.6%, 9.5% respectively, 

### p>0.05for both). for Arrangement 

### 2, both night and daytime reductions combined to give a cumulative percentage decrease of 55.9% 

### (p<0.05) by the end of the trial period. The degree of reduction is seen to diminish with time; for Arrangement 2, the reductionstarted at around 

### 80%. (ii) 

### Sprat: Duringthe first part of the trial (Arrangement 

### l), the reduction effect on sprat was highly variable and not significantly different from zero 

### (I 1.2%’ p0.05). Arrangement 

### 2 showed an immediate improvement 

### in system performancefor this species, the cumulative mean beginning at around an 80% reduction (pgO.05) and declining to 60.1% (peO.05) by the end of the trial. 

### Overall, both night and day sampling periods displayed a reduction in catch during periods 

### in which the sound projectors were 

### in operation, although the effectwas marginally strongerduringthe nightthan the day.

FAWLEY aquatic research laboratories Ltd 7(iii)Herring: The system was effective against herring with both sound projector arrangements, with a mean 56.2% (p<0.05) reduction for Arrangement 

### 1 and 79.3 % (p<0.05) for Arrangement 2. There was little discenible difference between day and night performance. The reduction 

### in effectiveness with time was less marked 

### in herringthan 

### in the other species. (iv) Whiting: For Arrangement 

### 1, a reductionwas seen only 

### in the night-time catch (58.2%,p<0.05 

### ). The latterwas the dominant element and was highly variable, 

### so that there was no significant effect on the overall catch caused by the acousticsystem (-31.9%, ~70.05). With Arrangement 

### 2, the day-night difference disappeared, and a mean reduction for the period of 

### 53.5% was found (p<0.05), againwith a decliningtrend overthe test period. (v) Other species with swimbladders (excluding lesser sandeel): 

### Both the nighttime and daytime catches showed reductions when the acoustic deterrent system was 

### in operation, averaging 40.8% (~~0.05) for Arrangement 1 and 54.7% (peO.05) for Arrangement2. Effectivenessdeclinedwith time. (vi) Other species without swimbladders: Small 

### but non-significant (p>0.05) reductions were seen 

### in species not possessing a swimbladder. The pattern was essentiallythe same for day and night-time periods. 

## 3.3 

## Length Distributionof the Catch Analysis of the length/frequency data was performed on the three most abundant species (sprat, herring and whiting), along with other species 

### for which sufficient data were available (flounder, plaice, 5-bearded rockling, pollack, dab andviviparous blenny. The data are graphically represented 

### in Figure6 (a

# - i). It is shown that: (i) significantly smaller whiting (- 4.05 mm; p 0.01) and plaice (- 

### 3.11 mm; 

### p < 0.01) were caught during sound-on periods; (ii) significantly larger 5-bearded rockling (+ 6.23 mm; p < 0.05) were caught during sound-on periods. These differences are small relative to the mean sizes of the fish. 

### 3.4 

## Catch Weight Totalweights of fish caught during the survey were not measured directly but may be estimatedfrom sample figures. The mean fish weights for sprat, herring andwhiting are given 

### in Table 3. Other species represent a negligable contributionto the overall catch weight and are not therefore shown. An estimate may be made of the expected reduction 

### in overall catch weight 

### for these three species during sound-on periods on the basis of operation 

### of the final configuration of the acoustic system in that period. From this, it is calculated that the observed catch of these three species of 503.11 kg would decrease to 155.9 kg, a reduction of 69%. Forthe clupeids (sprat and herring), a 73.3% reduction is indicated.


### 4 

## ISC CUSS ION The acoustic deterrence trials at Hartlepool Power Station have confirmed initial indications from earlier experiments carried out for Nuclear Electric plc, at Otdbury Power Station (Thatcher and Irving, 1992) that acoustic methods can be used effectively to reduce the impingement of fish at coastal power stations. The overall
FAWLEY aquatic research laboratories Ltd 8reduction 

### in fish numbers achieved was 51%, while for sprat and herring, the chief problem species for 

### UK coastal power stations, numbers caught were reduced by 60.1% and 79.3% respectively. 

### Inweight terms, this amounted to a 73.3% reduction 

### in the combined sprat and herring catch. With improvements 

### in the sound projector configuration and hardware design, considerably better performance than this should be achievable. It is clear from these data that coastal power station sites can benefit from acoustic deterrent systems with performancefigures comparable to those found in successful freshwater applications of the technique. For example, 

### in trials of a similar system carried out for the National Rivers Authority on a river pumping station in York, England

(30 m3

### s

# *'maximum discharge), entrainment rates of coarse fish (mainly cyprinids) were reduced by 80%, even when fish swimming would have been severely impeded by lowwater temperatures, of 

### 4

### OC(Woodet 

### a/., 1994); this has ledthe NRAto install a permanent system, and to fund further trials to extend the range of possible freshwater applications. 

### In the most recent trial undertakenfor the 

### NRA, the Institute of Freshwater Ecology have reported a 92% diversion efficiency for salmon (Salmo salar) and sea trout 

### (S. 

### frutfa) smolts 

### (Dr 

### S. Welton, pers.comm.). 

### In other countries, researchers have also reported high success rates with acoustic deterrent systems in freshwaters (Norway: 98% with S. 

### salar: Knudsen et a/., 1994; USA: 60-loo%, various spp.: Loeffelman et a/,

### 1991a,b; Klinect

### ef a/., 1992). 

## 4.1 Species 

## Differences Considerable variation 

### in response was found amongst the species observed. These may be relatedpartlyto anatomicaland partlyto behaviouraldifferences. Anatomical differences which infhence the hearing capabilities of different species, and hencetheir capacityto respond to acoustic signals, are welt documented (see e.g.* review by Hawkins, 1986). An obvious fundamental difference exists between those species which have a swimbladderand those not possessingone. This organ acts as a sound-pressure-to-particle-motion transducer, and possessing one has been shown to confer an increase of around + 20dB in hearing sensitivity in some species. It is therefore logicalto expect the difference 

### in results shown for example in Fig 5 (e) and 

## (9 between the species with and without swimbladders. Any effect found with the nonswimbladder species (bottom-living types: chiefly flatfish) may have been due to vibrations propagated along the seabed (on which the outer sound projectors were located), rather than sound pressure fields propagated via the water: the flatfish auditory system is receptive principally to particle motion and not to sound pressure (Hawkins 1986). 

### Within swimbladder-possessing species, variations arise from differences 

### in the fine structure of the inner ear and the swimbladder, and the mechanical efficiency of the coupling between the two. 

### Both the gadid (cod, whiting) and clupeid (herring, sprat) families have been found previously to be sensitive to sounds 

### in the 50-600 Hz frequency range employed at Hartlepool (Schwartz and Greer, 1984; Hawkins, 1986) and to show avoidance reactions when exposed to a similar deterrent signal when applied 

### in the laboratory (Tumpenny et 

### al., 1993, and additional unpublished data). However, the variation in degree of responsiveness has not before been evident: the Hartlepool results show herring to have reacted more strongly than sprat or whiting (79.6% reduction,versus 60.1 % and 53.5% respectively). This 

### is most clearly 

### shown by the fact that herring were also strongly affected by the initial, weaker sound field associatedwith the sound projectorArrangement I. While no satisfactory explanation
FAWLEY aquatic research taboratories Ltd 9can be provided at present for this substantial difference between 

### two closely related species (sprat and herring), auditory anatomy may differ; also, differences 

### in swimming capability associatedwith the largersize of the herring (mean 

### 97 mm versus 81 mm for sprat, which would yield a 20% increase in speed of the herring over that of the sprat) may have contributed, although, size-for-size, sprat and herring have very similar swimming performance(Turnpenny, 1983). 

### 4.2 

### Day/Night Differences Although for the overall combination of species the effectiveness of the sound system was similar by day and night (Figure 5 a), marked differences are seen for some individual species. The most notable case is that of the whiting for the initial sound projector arrangement (Figure 

### 5 d). This day /night difference disappeared with the revisedsound projectorarrangement. At present, no satisfactoryexplanation can be advanced for these findings. 

### 4.3 

### Size

# - Related Differences The significant (p<0.05) differences in mean size of fish caught during sound-on versus sound-off periods 

### in some specieswere small and of no practicalsignificancewithin the present study. The size of the differences may however have been constrained by the limited range of fish sizes and age groups present and possible size-related effects should be considered 

### in any future studywhere a greater rangeof sizes is represented. 

### In a paratle'l situation, it has been shown that the larger gadoid fish showed a greater tendency to be repelled by underwater sounds emitted by seismic airguns during oil and gas exploration (Engss 

### ef a/., 1993). 

### 4.4 

### Scope for 

### Improvementat Hartlepool A number of partial sound system failures occurred during the first few days of the trial. These were due mainly to amplifiers overheating owing to inadequateventilation. The problem was quickly corrected by increasing ventilation within the amplifier rack; as a further precaution, self-resetting thermal overload cut-out switches were fitted to prevent amplifier damage. No further problems were found. System availability (as sound-projector-days) over the whole period was 86%.; during the final sound projector arrangement (Arrangement

### 2), Le. after the initial problems had been solved, availability rose to 100%. The problem of air 

### loss (Section 2.2) from the sound projectorsvia the cables should be addressed 

### in future applications. Itwas quickly recognisedthat the initial sound projector arrangementwas not optimal. This aspect underlines the importance of undertaking on-site measurements of background noise, to establish a baseline for the acoustic modelling: Subacoustech concluded that the PRISM modelling could have yielded 

### an appropriate initial sound projector configuration, had the background noise information been available (Petrie, Nedwelland Needham). Although a revised sound projector configuration was implemented, the arrangement chosen was a compromisewith the equipment available. A more effective arrangement proposed for future application would be to deploy all 12 sound projectors in midchannel positions to create a complete defensive arc so as to preventfish entry via the sides of the channel (Figure 7). The sound projectors located 

### on the intake are

FAWLEY aquatic research laboratories Ltd 10believedto have been largely ineffectiveas 

### a result of the very low signal-to-noise ratio 

### in the key frequency range. The problem of air loss from the sound projectors mentioned 

### in Section 

### 2.2,and the consequent reduction in the sound pressure levels generated, is considered to have been responsible for the declining effectiveness of the acoustic deterrent system over the course of the trials. It isthought unlikelythat physiological adaptation (‘habituation’) by the fish played a part, as the large tidal excursions (several kilometres per tide) make it unlikely that fish would remain in the area for long enough to adapt; the laboratory experiments showed that habituation was not apparent over 2-3 days of repeated exposure (Turnpenny et a/., 1993). It can be surmised that better results could be achieved, even with Arrangement 

### 2 of the sound projectors, as used in the latter part of the survey, provided that 

### full performance of the sound projector units were maintained. The performance figures given in Table 

### 2 are the means for the whole of the latter period 

### (25 March

# - 12 April), and cover a declining trend 

### in source level (see Section 

### 2.3). The average efficiency at the start of this period was around 8O%, and declined to 50% by the end of the survey The problem of air loss via the sound projector cables has been addressed in laterversions of the 

### FGS30/600unit 

### 4.5 

## Impact

# on the Local Seat Colony The study undertaken by INCA (Wilson 

### ef a]., 1995) monitored the behaviour of the Seal Sands colony of grey seals during the trials, and compared their patterns of behaviourwith that recorded in previousyears. The report concluded that: 

### i) there was no detectable effect of the sound system on seal numbers or behaviouron sound-on comparedwith sound-off days; ii) during sound-on days, the seals rarely approached the sound sources, but showed no 

### signs of alarm caused bythe sound when 

### in the water either; iii) any effects due to the sound system ‘paled into insignificance’ compared with more overt disturbances, e.g. from bait-diggerson Seal Sands. Infinal conclusion, DrWilson states that the seal monitoring programme “succeeded 

### in allaying fears of any obvious major effect on the seals” and that ”there would appear to be no objection from the seals’ point of view



## ... to this device being permanently installed”.


### 5 CONCLUSIONS 1. The acoustic deterrence system proved effective as a means of reducing fish catch, as trials elsewhere at freshwater locations have shown. The highest effectiveness (6040% reduction, p<0.05) was against the clupeid species, sprat and herring, which are most numerous in the 

### CW screen-catches of most British coastal power stations. Other species possessing a swimbladder were also strongly repelled 

### (-54% reduction, p<0.05), whiie non-swimbladder species showed only a modest response (16% reduction: p>0.05). The swimbladder 

### in fish is known to play an important role in hearing. 2. The positioning of the sound projectors was found to be critical. High background noise levels generated by the pumps, within the 0-600 Hz range 

### of the deterrent signal, were found to interferewith the signa! when the majorityof the sound projectors were placed nearto the intakes. The use of acoustic modellingenabled new
FAWLEY aquatic research laboratories Ltd 11configurations to be assessed quickly and efficiently and led to a successful final outcome of the trials. 3. The reliabitity of the sound generating system was found to be far superior to that experienced in previous trials at Hinkley. The overheating problems found during the first few days of the trials were quickly overcome by improving ventilation. A problem 

### of air

### loss from the sound projectorscaused by leakage via the cables did lead to a progressive reduction in sound output and would need to be eliminated 

### in any permanentsystem. 4. No adverse effects of the system on aquatic wildlife were evident. An independent study of the local seal colony arranged by English Nature revealed no disturbance as a result of operating the sound system. The implementation of any permanent acoustic deterrent system would be expected to have an overall benefit to localwildlife andfisheries through the reduction 

### in fish mortalities at the power station.



### REFERENCES Blader, 

### J H 

### S, 1981. The swimbladder and hearing. 1n:Hearing and 

### Sound Communication 

### in Fishes. Springer-Vedag, NewYo&, pp 109-133. Campbell, R C, 1974. Sfatisfics for Biologists. University Press, Cambridge. EngAs, Lerkkeborg, S and Soldal, A V, 1993. Effects of seismic shooting on catch availabilityof cod and haddock. Instituteof Marine Research, Noway, Fisken og Havet, 9, 117pp. Hawkins A 

### D, 1986. Underwater sound and fish behaviour. In: The Behaviour of Teleost Fishes, (Ed. Pitcher, T J), LondonCroom Helm, pp 114-151. Klinect 

### D A, Loeffelman 

### P H & Van Hassel 

### J H, 1992. 

### A new signal development process and sound system for diverting fish from water intakes. Proc. Amer. Power Conference, Illinois Institute of Technology,April 13-1

### 5, 1992, Chicago, Illinois. Knudsen, F

### R, Enger, 

### P S and Sand, 0, 1994. Awareness reactions and avoidance responsesto sound injuvenileAtlantic salmon. J. Fish Biol., 45 (2), 227-233. Langford, 

### T 

### E, 1993. Elecfticity Generation and the �co/ogy of Natural Wafers. University Press, Liverpool, 342 pp. Loeffelman 

### P 

### H, Van Hassel

### J 

### H & Klinect 

### D A, 1991(a). Using sound to divert fish from turbine intakes. 

### Hydm Review, October 1991, pp 30-43. Loeffelman P H, Klined 

### D A & Van Hassel 

### J H, 1991(b). Fish protection at water intakes using a new signal development process and sound system. In 'Waterpower '91', Amer. SOC.Civ. Engrs, pp 355-365. Petrie

### JE, Nedwell

### J & Needham K, 1995. Acoustic surveys of a 

### fish deterrent system at Harttepool Nuclear PowerStation. Subacoustec report no. CNAI84ROI02 Schwarz, A L and Greer, GL, 1984. Responses of Pacific hemng (Clupea harengus Pallasi)to some undewatersounds. Can. J. Fish. Aquaf. Sci.,41, 1183-1 192.

FAWLEY aquatic research laboratories Ltd 12

### Seaby, R M H, 1994. Survivorship trial of the fish return system at Sizewell 

### B power station


## . FawleyAquatic Research Laboratories Ltd, Reportto Nuclear Electric plc, No. FCR 102/94. 

### Thatcher K P & 

### Irving 

### P, 1992. Fish deterrent trials at Oldbury Power Station, November I991 to January 1992. FawleyAquatic Research Laboratories Ltd, Reportto National Power plc and Nuclear Electric 

### PIC, No. FCR 009/92. 

### Tumpenny, A W H, 1981. An analysis of mesh sizes required for screening fishes at water intakes. 

### Estuaries4 (4), pp 365-368. 

### Turnpenny, A 

### W H, 1983. Swimming performanceofjuvenile sprat, Spmttus spmaffus L., at different salinities. J.

### fishBiol., 

### 23, pp 321-325. 

### Tumpenny, A 

### W H, 1988. The behavioural basis of fish exclusion from coastal power station coolingwater intakes. CEGB Internal Publication No. TPRD/L/2657/N84. 

### Tumpenny, A 

### W H, 1993. Bubble curtain fish exclusion 

### trials at Heysham 

### 2 power station, February 1993. Fawley Aquatic Research laboratories Ltd, Report 

### No. FCR 037193. 

### Turnpenny, A 

### W 

### H, Utting, 

### N J, 

### Millner, R S 

### and RiJey, J 0, 1983. The effect of fish impingement at Sizewell A power station on North Sea fish stocks. CEGB Sizewell 

### B Public Inquiry Supporting Document No. S380. 

### Turnpenny, A W H and Coughlan, 1992. Power generation on the British coast: thirty years of marine biological research.

### Hydrecol. Appl., 4, pp. 1-11. 

### Tumpenny, A 

### W H 

### and Henderson, 

### P A, 1992. Design and testing specificationfor a fish deterrent bubble barrier for Heysham Power Stations 

### 1 & 

### 2. Fawley Aquatic Research Laboratories Ltd, Reportto Nuclear Electric plc, No. FCR 006/92. 

### Turnpenny, A 

### W H, Thatcher, K 

### P, Wood, R and Loeffelman, 

### P H, 1993. Experiments on the use of sound as a fish deterrent. Fawley Aquatic Research Laboratories Ltd., Contractors Report to the Energy Technology Support Unit 

### (ETSU), Harwell, Didcot, Oxfordshire OX1 1 ORA, Rept. 

### No. 

### ETSU T/04/00171/REP. 

### Tumpenny, A 

### W H, Thatcher, K P, 

### Wood, R and Nedwell, J, 1994. Fish deterrent field trials at Hinkley point power station, Somerset, 1993-4. Fawley Aquatic Research laboratoriesLtd 

### , Reportto Nudear Electric plc, No. FRR 132/94. 

### Wilson, S, 

### Cook, M, Grellier, 

### K, Leakey, M, Mathwin, 

### S, Muir, D and Parfane, S, 1995. Monitoring of seals at Seal Sands during the Acoustic Fish DeterrentTrials (27th Februaryto 13thApril, 1995). Report

### to Nuclear Electricplc, May 1995. 

### Wood R, 

### Thatcher K 

### P, Woodcock A & 

### Turnpenny A W H. 1994. Fish deterrent trials at the River Foss pumping station, 

### York, 1993-1994. Fawley Aquatic Research LaboratoriesLtd, Report 

### No. FIR 087/94.

~~ FAWLEY aquatic research laboratories Ltd 13f . ­ j f

i *\

1' 

## f Hartlepool 

### f Tees Estuary j 

### ___

..--.----.-.---

.-_..I___.___..___



### Figure 1 

### Location Map Showing 

### Hartlepooi 

### Power Station

### and Environs

### ......................................... 

### ......................................... 

### ......................................... ......................................... 

### ......................................... ......................................... 

### ......................................... 

### ......................................... ......................................... .........................................

.................................... 

### .................................... ....................................



### ................................. ................................. 

### ................................. .................................

.............................. 

### .............................. .............................. 

### .............................. ........................

....................



### ...............................



### ..................................... ..................................... 

### ..................................... ..................................... ..................................... ..................................... ..................................... ..................................... 

### ..................................... ..................................... ..................................... 

### ..................................... ..................................... .................................... 

### ..................................... 

### ..................................... .........................................



### .................................... 

### .................................... ....................................



### .................................



### .............................. ........................



### ....................

...............................



### .................................... ..................................... 

# --kN

Drum Screens

Trash Basket



# @ Sound ProjectorArrangement 1 Scale 

### 1 50 

### m i Additional Sound Projectors,Arrangement2

Notes:Mid-channelsoundprojectorpositions wereeach occupiedby 

### two unitsmountedon asingleframe Depths shown as ChartDatum.



### Figure 2 Map 

### of Hartlepool Cooling Water intakeChannel showing Bathymetry and the 

### Two Arrangements 

### of Sound Projectors

### Total 

## Numbers of 

### Individualsfor 

### Key Species 

### Recordedfor

### Test 

### and
Control 

### Periods Corn

### bined, and Minor 

### Species 

### Recorded.

ALL DATAADJUSTEDFOR 3 RUNMNG CWPUMPS

# - IGNORES IST MARCH SAMPLE 

### Species 

## Sprat Herring 

### Whiting 

### Sand 

## eel Flounder 

### Plaice Stickleback, 3-sp. 

### Rockling, 5-B Goby, SP 

### Lesser

### weever Dab 

### Vivaparous 

### blenny Pollack 

## OTHERS TOTAL 

### Scientific 

### Name
Sprattussprattus 

### Ciupeaharengus MerJangius merlangus 

## Ammodytes tobianus Platichtbys fiesus 

### Pieuronectesplatessa Gastervsteusaculeatus Cilia fa mustela Gobidae Echiichthys vipera Limanda limanda Zoarces viviparus Pollachiuspollachius

ADDITIONAL

### MINOR SPECIES (uncorrected1 

### Saithe Cod Hooknose 

### Sea 

## scorpion Northern 

## rockling Bull-mut Sea trout 

### Common 

### eel Pollachius virens Gadusmorhua Agonus cataphractus 

### Taumlusbubalis 

### Ciliata septenfrionalis Myoxocephaius 

### Scorpius 

### Saimo trutta Anguilla anguilla Total 

## YO of Total

486

### 13 43.55 4603 

### I 41.23

8624 

### 7.73 2210 

### I .98 

### 1942 1.74 1198 1.07

868 

### 0.77 431 

### 0.39 

### 408 0.36 

### 256 0.23 214 

### 0.19 

### 164 

### 0.15 407 

### 0.09 564 

### 0.52 1 

### 'I1630

95 

### 73 64 49 

### 37 34 33 

### 24

### Table I lumpsucker 

### Gyclop 

## fernslumpus 24 Dover sole 

## Solea solea 23 Greater pipefish 

## Syngnafhusacus 20 Witch 

### Glyp 

## fucephaluscynogiossus 13 Greater sandeef 

## Hyperoplus lanceolatus 12 Butterfish 

## Pholisgunnellus 8 Pearlsides 

## Maurolicusmuellen 7 Dragonet 

## Callionymus lyra 

### 7 Stickleback, 

### 15sp. 

## Spinaehia spinachia 6 Sand smelt 

## Atberina boyeti 5 Dogfish 

## Scyliorhinuscaniculus 4 Grey gurnard 

## Euttigla gumardus 4 Common 

### sea snail 

## Liparis lipatis 3 Cucumber smelt 

## Osmerusepedanus 3 

### Atlantic salmon 

## Salmo saiar 2 Tadpole fish 

## Raniceps raninus 2 Nilsson's pipefish 

## Syngnathus rostellatcrs 2 

### Brill 

## Scophthalmus rhombus 1 Lemon sole 

## Microstomus kitt 1 Turbot 

## Psetta maximus I Ballanwrasse 

### Labrus 

## bergylta 1 Golden grey mullet 

## Liza aurata 1 Thick-lipped mullet 

### CheionIabrosus 1 Noway 

### pout 

## Trisopterusnorvegicus 1 Lamprey 

## Lampetraf-luviatilis I Worm pipefish 

## Nerophis hmbriciformis I 

### Angler 

### fish 

### Lophius

## piscatorius 1Table 2 Mean Reductions in Fish Catchwith the Acoustic Deterrent System Operating, for Each ofthe Two Sound ProjectorArrangements (see Figure 2). 

# 1 Period

Reduction Significance Reduction significance Reduction Significance Reduction Significance

# 1 Arrangement I

Smcies All Species

sprat Herring
Whiting 

# 1 Arrangement2

* 1-24 Marc Night 0.1%
ns -36%
ns 34.1% * -39.1 %
ns 32.4%
ns 24.5%
ns ns 52.3% 39.5% 53.0% 62.1% 54.7%
ns nS 31.2% 25.9% 17.0% 2.2% 15.6%
ns ns ns ns ns Other Species Reduction with Swimbladder Significance Other Species Reduction without Swimbladder Significance 

### Note: negative vaiuesindcafe 

### inceasedcafch
Significance

### levels: 

### ns= p>0.05



### =p<0.05

!

FAWLEY aquatic research laboratories itd 

# I I

# Control Unit


# I FGS400 

# FGS 400

A 

# Amplifier Amplifier

FGS 

## 30/600 30/600 

## Sound Sound 

## Projector Jrojector 

# FGS 400 FGS 400 

# Amplifier Am

# plif 

# ier

Note: Onlytwosoundprojectorsare shown; eachamplifierwas connectedto twosound projectors. Thenumberofunits shownrelates to Arrangement 7; twomoreamplifiers andfour additionalsoundprojectors were usedin Arrangement2.


### (a) Block Diagram 

### of Sound Generating System Components.

I--.-.--- 

# Y

\ 

## E t 

## 2 D -".__-_.I_ -....-_.­ 

### 2 L 

# oL 1 I I I I 

## I 0 

### 0.2 

### 0.4 

## 0.6

. 

## 0.8 1 

### 1.2. Time/ seconds


### (b) Graphical Representation 

### of the 'Empirical Series

## No 7' Deterrent Signal

Figure 

### 3 

### The Sound Generating System 

### and Acoustic Deterrent Signala, a,

v) v) U 0 'C 

# a= a, 

## 0 a U 

### c 

# 8
3 U U S S 0 3 

### m 

## m 0 (13 U S 

### m 

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### * 

## 3 w v) + 

## I # S 0, 

## F ii

## Figure 

## 5 Cumulative Mean Percentage Reduction in 

## Fish Catch for Sound Projector Arrangements 1 

## 812

Species: All Combined

Arrangement 1 i- Arrangement 2

Species: Sprat 1

0.5

0

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## - April 1995 -Night +Day -24-hour

## Figure 5 

## (continued)

Species:Herring

Arrangement 1 i- Arrangement 2

Species:Whiting

-Night -+-Day -24-hourU

Date: 

## Figure 

## 5 

## (Continued)

Speciw: otherSpecies,withswimbladders 1

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### 4 0.5 

# s t $ 0 .fl 

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-1 123 4 5 6 7 8 9 IO11121314U1611l119M21ZO~(i21261728293031 1 2 3 4 5 6 7 8 9 101112 Date: March

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Species: other Species,withoutswimbladders 1

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## I

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# @ Framewith Two 

### SoundProjectors
* Scale 

### 1 50

### m 

### 1

Figure

### 7 Proposed PermanentArrangements

### of Sound Projectors

## Appendix 1

Day, Night

### and 24-h 

### Numbers

### of Fish 

### lmpingedfor 

### Sound-on and Sound-offdays

FAWLEY aquatic research laboratories Ltd 1

## Appendix 1

Day, 

### Night and 

### 24-hNumbers

### of

### Fish Impinged

### forSound-on and Sound-offdays

FAWLEY aquatic research laboratories Ltd 1

### All SDecies 

### CombinedSwatHerringWhiting

### Other suecies: with swimbladderOther species, without swimbladder

# Acoustic Surveys of a 

# Fish Deterrent System at 

# Hartlepool 

# Nuclear Power 

# Station

Report no. 

### CNA184R0102

anproved for release 

### J 

## E Petrie
J 

### Nedwel
and


## K Needharn

J Nedweii, principal Consultant July 1995AcousticSurveys of aFish DeterrentSysteiti nffiartlepoolNuclearPower Station



### Contents



### 1.

2.
2.1
2.2

3.


### 3.1


### 3.2

4.

5. 

### List 

### ofFigures

introduction

Environmental Survey
Measurements
Results



### Locai 

### Sound Field Survey
Measurements
Resu1

### ts

Discussion

Conclusions

List 

### of Figures 

### 2



### 4

5


### 5
6



### 9
9


### 9

12

13



### 14


### 15
16


### 17
18 

### Figure 1 

### Map of Seaton Channel and environmental survey measurement positions Figure2 

### Table ofenvironmental survey overall broadband sound pressure levels Figure3 

### Graph

### of fiequency spectra 

### oftime histories 

### for positions 

### Ib and 2 Figure

### 4 Graph

### offrequency spectra 

### oftime historiesfor 

### positions 3 

### and 4 

### Figure 5 

### Graph 

### offrequency spectra 

### ofthe source levels along the inlet channel centreline 

## 2
Document CN'i81ROiO2AcousticSurveysofa

### Fish DeterrentSystem at IinrrtEpoolNuclearPowerStation



### Figure 6 

### Graph ofthe broadband sound pressure levels dong the inlet channel centreline Figure 7 

### Graph 

### offrequencyspectra oftime historiesfor positions

### E and 

### F Figure 8 

### Graph 

### of sourcelevel frequency spectraalong400m 

### of SeatonChannel Figure

### 9 Graph

### ofthe broadband sound levels along 

### 4001x1 

### of SeatonChannel Figure 10 

### Graph offrequency spectraoftimehistories for 

### positions

### D and 

### G Figure 11 

### Graph offrequencyspectra oftime histories for positions laand lb Figure 12 

### Map 

### ofthe water inlet channel Figure 13 

### Table ofthe broadband sound pressurelevels in 

### the water inlet channel Figure 14 

### Graph ofthe broadband sound pressurelevels in the water inlet channel Figure 15 

### Graph offrequency spectra 

### oftime historiesrecorded inpositions 1-1 

### to 1-5 Figure 16 

### Graph 

### offrequency spectra oftime historiesrecorded in positions 1-1 to 1-5 Figure 17 

### Graph 

### ofeequency spectra oftime historiesrecorded in positions 2-1 to 2-5 Figure 18 

### Graph 

### offkequency spectra oftime historiesrecorded in positions2-1 to 2-5 Figure 19 

### Graph 

### offrequency spectra oftime historiesrecorded 

### in positions3-1 to 3-5 

### Figure 20 

### Graph 

### offrequency spectra 

### oftime historiesrecorded in 

### positions 3-1 

### to 3-5 Figure 21 

### Graph ofbroadband sound pressure levels along the centre 

### ofthe inlet channel

~~ ~ 

### 3 19


### 20
21


### 22
23
24


### 25
26
27


### 28
29
30
31


### 32
33
34

Subucoustech Ltd 1995 Document CNAI84ROf02AcousticSiirveysof aFish DeterrentSvsrettl utIfartlepool iVucleurPower Station



### 1. Introduction
SubacoustechLtd were tasked by Nuclear Electric 

### PLC to study the sound field produced by 

### an acoustic fish deterrent system

. 

### The system was installed in Seaton Channel, a part 

### of the River Tees 

### Estuary, by 

### Fish Guidance Systems Ltd 

### in February 1995 for 

### a trial period to reduce the numbers 

### of fish entering the intake 

### for the condenser cooling water system 

### ofHartlepool Nuclear Power Station. 

### A map 

### ofthe sitemay be seen 

### in figure 1.
Prior to the installation of 

### the deterrent system, acoustic modelling had been carried out using the SubacoustechLtd PrISM model. This led to a configuration 

### of eight 

### model 30­ 600 

### sound projectors. Six 

### ofthese were placed along the water intake wall and a further pair 

### ofprojectors was installed at the mid-point 

### ofthe entrance to 

### the water inlet channel. These projectors emitted a series 

### of acoustic signals which research had shown to deter fish &omswimming toward the signal source [Turnpenny et uZ 19941. 

### An acoustic survey was required to ensure that sound pressure levels were contained within the inlet channel and that significant sound levels did not extend to the local seal population 

### on the opposite side of Seaton Channel. 

### This survey was performed 

### on 12th

### March 1995 

### after someinitial measurements had been performed 

### on 8th March 1995. 

### At the time 

### of measurement, projectors 110.3

### and no.5 

### had been displaced by water flow 

### to positions directly in front 

### of two of the water inlets, the high 

### water inflow subsequently altering their radiation characteristics. These two sound projectors were therefore deliberately disconnected 

### from the system to avoid the behaviour of the system being compromised. The survey demonstrated

### high background levels closeto the power station water pumps. 

### Following Grther acoustical modelling, a revised projector arrangement was devised involving the addition offour more projectors, 40m 

### along the inlet channel 

### from the water intake. 

### A second survey was then undertaken after the system had been renovated at the end of the trial on 

### 17th May 1995 

### to record the acoustic field generated by the revised sound projector configuration.



### 4
Subacousrech Ltd 1995 Llonmmenr CNA184R0102AcousticSiirveys of nFish Deterrent,!+stem atIfortiepoolit'uclear PowerStation



### 2. 

### Environmental 

### Survey
2.1 

### Measurements 

### Recordings ofthe sound field on the bed ofthe channel and also at the wall on which the water intake is located were made using a Bruel and Kjaer type 8103 hydrophone (serial 

### no. 1013189). The hydrophone output was fed into a Subacoustech low noise voltage 

### amplifier type SAVOlO (serial no. 040), 

### the output of which in turn was fed to a Sony portable DAT recorder type TCD-D7 (serial no. 73734). With the exception 

### of the hydrophone, which was mounted externally, the equipment was housed in a Subacoustech portable hyperbaric pressure vessel. In the case ofthe recordings made at the water intake side wall, the equipment was simply lowered into the water fiom the top ofthe wall. For the measurements taken at the edge of

### the water inlet channel and 

### in SeatonChannel, the equipment was lowered onto the bed of the channel at each position from the Boy Andrew, a workboat that had been used also for the installation 

### of a number of the projectors. The workboat was fitted with Furuno radar instrumentation type FR-603D (serial 

### no. ADB9ZWFR603 1) 

### which enabled accurate positional data. The recordings made from the Boy Andrew were made within 2.5 hours either side 

### of high tide as required by English Nature to prevent any disturbanceto the seal population which tended to use the channel at times oflow water.
A total 

### of fifteen sets of measurements were taken at fourteen different positions in or around the power station intake, a map of which may be seen in 

### figure 1. Since measurements could only be taken in the channel at times of high water to prevent disturbingthe seals, recordings were made on 8th March 1995

### of sound pressure levels off the water inlet channel side wall at positions la and lb during different tidal conditions. Further recordings were made on 12th March at various positions in Seaton Channel. These are 

### shown in figure 1 as positions 2 

### to 4 

### which were situated along the axis 

### of the water inlet channel and positions 

### A to 

### J which formed a line 

### of measurements across the 

### axis ofthe inlet channel along a 1 1

### OOm stretch of Seaton Channel.
The recordings made were calibrated using a 1V, 1

### OOOHz signal from a Hewlett Packard type HP3301A signal generator and a Goldstar 20MHz 

### type OS-9020A oscilloscope (serial 

### no. 4010355) which was also used for initial sound pressure level analysis.
The DAT recordings were subsequently analysed using computer software and were auditorilyexaminedby means 

### of an Audio Technica full range speaker system. 

### In addition to 

### these recordings, a chain 

### of four Subacoustech type Hp02 

### hydrophones were laid along the length of the inlet channel and into the main water channel to enable sound level monitoring during the run up period ofthe installation. Unfortunately due to the presence 

### of high level electrical return current to the power station in the water, intederence was present to such an extent that no useful results could be obtained from 

### 5
Subacoustech Ltci 1995 Document ChA184RO102AcousticSus'unwys ofa Fish Deterrent Xvstetn crt Hartlepool NuclearPower Station



### these hydrophones and reliance was instead placed 

### on the submersible measurement equipment.
2.2 

### Results
Two lines 

### of measurements were taken for the environmental survey. Positions 2 to 4 

### were situated along the 

### axis of the water inlet channel. Measurements were made at positions A to 

### J across the 

### axis ofthe water inlet channel, donga 1lOOm 

### stretch 

### of Seaton channel. Figure 2 

### is a table 

### of the results of the measurements 

### of the overall broadband sound pressure levels made for the environmental survey. Along the 

### axis ofthe water 

### inlet channel 

### it can be seen that the 

### signal strength was only 

### 8dB above background at 100m. 

### Sincethe signal to noise ratios at positions 

### E and 

### G are OdE3 (Le. the signal has decayed to the normally occurring level of sound) the attenuation experienced by the propagating deterrent signal was sufficient to reduce the sound pressure level from the system to that ofbackground within 

### lOOm to the east and 

### 200m to the west 

### ofthe water inlet channel. It 

### is clearthat the acousticfield was extremely weil confined within the inlet channel.
The background noise 

### in and around the water inlet channel was high and audibly extremely simiiar to the airborne noise in and around the power station pump house. The pumps were situated directly behind the water inlet channel and were clearly the main source 

### ofthe waterborne background noise. Figures 3 

### and 

### 4 are frequency spectra 

### oftime histories recorded in the measurement positions lb, 2, 

### 3 and 

### 4 which represent the positions closest to the power 

### station. Strong peaks at 25Hz, 50Hz 

### and 300Hz 

### are evident in the plots, characteristic 

### ofthe noise from the power station. It is also clear 

### from these 

### two graphs that the background noise at the water intake, the edge 

### ofthe water inlet channel and lOOm 

### fiom the water intake along the inlet channel centreline were 

### of sbir6lar 

### levels. However 150m 

### away from the intake, along the inlet channel centreline, the background noise level drops considerabfy. 

### This is to be expected since the geometry 

### of the water inlet channel is such that sound energy is likely to be codined 

### within it 

### by the mud banks on either side, whereas in Seaton channel the 

### sound would be able to spread with consequent reduction in level.

. 

### This confinement to the water inlet channel is supported by figure 5 which presents ftquency spectra of 

### the source levels along the inlet channel centreline and figure 6 

### which is a graph 

### of the broadband sound pressure levels at the same positions. The Ievels at 

### positions 1 

### and 3 

### are 

### similar. The frequency spectra 

### ofposition 

### 2 indicated that the source levels were higher

. 

### Since position 2 was close to a pair 

### of sound projectors this 

### is to be expected. Thebroadband sound pressure levels suggest that position 1 

### is higher but 

### this 

### is because 

### of high background peaks at 25&, 

### 50Hz and in particular 300Hz. 

### However, the main observationthat can be drawn 

### is that the levels 

### for position 4 are considerably lower than the levels at the other three positions nearer the power station water intake. Evidently the propagation 

### of both background noise and the deterrent signal was well confined along the

### line of the 

### water inlet channel up to 100111, 

### 6
SubacoustechLtd 1995 DocumentCNA184ROIO2AcousticSimeysof n

### FishDeterrent $yStelil utffartkpooi NudearPowerstation



### Figure 7

### presents spectrafor positions 

### E and 

### F which were in Seaton channel, 1OOmeither side 

### ofthe inlet channel centreline. The results obtained at these points indicate broadband signal to noise ratios of OdB and 2dI3 

### respectively. These can be compared 

### to the 8dB 

### signalto noise ratio obtained for position 

### 4 which was along the inlet centre line. Position 

### 4 was actually hrther away from the water intake. 

### This 

### is best illustrated 

### by figure 8, 

### a graph of source level frequency spectra along 400m of Seaton Channel and figure 9, 

### a graph ofthe broadband source levels ofthe same area. Both plots indicate that the sound levels along the 

### axis of the water inlet channel are well above those for the positions elsewhere along SeatonChannel. Figure 10 

### is a graph of frequency spectra of measurements taken at positions 

### D and 

### G, with the system 

### on 

### and also with the system OKThe levels with the source 

### on at position 

### G appear higher than background and would suggest a signal to noise ratio greater than 

### OdB. This however is not the case since the auditory examination of the recordings indicate that 

### no deterrent signal is present and the spectra ofthe recording with the system 

### on is characteristic 

### of background noise rather than resembling spectra of the deterrent signal obtained in other positions. An 

### increase in background noise level is therefore responsiblefor this anomaly. Although the reason 

### for this increase is unknown, changes 

### in background noise are common as a result of changes in wind speed or improved propagation 

### in patches ofhomogeneous water. Figure 1

### I presents fkequency spectrum analysis 

### of the recordings made at the water inlet channel side wall. It is interesting to note the difference between the two sets 

### of data. Although taken at the same point the measurements were taken four hours apart and therefore at different tidal conditions.For a fluid medium to propagate sound effectively it 

### is necessary 

### for the fluid to be of a depth of at least a quarter of

### the wavelength 

### of the required signal. Position lapresents measurements taken in water of a relatively shallow depth of 

### approximately 1.5m. 

### This 

### depth represents a quarter wavelength 

### in water of a frequency of

### 250Hz and it can clearly be seen that with the exception 

### offrequencies below 

### 50Hz relatively little propagation of background noise 

### or deterrent signal occurs below 

### 250Hz. This 

### can be compared to the data ofposition lbwhich represents data acquired at the same point but only 

### an hour before high tide, the water depth being approximately 

### 4m. This corresponds to a cut 

### offfrequencyof 1OOHz,

### which again is evident in figure 1 1. The propagation 

### of sound therefore is to some degree affected by the tidal conditions, lower water levels attenuatingradiation at the lower end 

### of the frequency spectrum. This effect was predicted by the PrISM model.
To 

### summarise, from the results of 

### the environmental acoustic survey, a number ofpoints can be noted. 1) 

### The ievel of

### the deterrent signal drops to that of 

### the background noise within 225m of the water intake.



### 7 SubaeoustechLtd 1995 DocumentCNA184ROl02

### 2) The background noise level 

### is high and mainly due to the noise emission from the 

### cooling water pumps. 3) 

### Both the background noise and signal propagation is extremely confined dongthe 

### axis 

### ofthe water inlet channelup to 100m. 

### 4) The sound propagation 

### fromthe water intake 

### is to a certain extent affected 

### by the tidal conditions, the lower frequenciesbeing attenuated at 

### low water.



### 8
Subacoustech Ltd 1995 Document CNA184RO102AcousticSirr?}eys ojuFish Deterrent Svsteni ut HurIlepoolIt’uclear Power Stution



### 3. 

### Locd SoundField 

### Survey 3.1 

### Measurements


### The acoustic measurements for investigation 

### of the local 

### sound field were made on 17th May 1995 

### using a Bruel and Kjaer type 8105 

### hydrophone (serial no. 1417794) suspended in the water from a dinghy at a depth 

### of 5m from the surface. The hydrophone

### was 

### linked to a Bruel and Kjaer charge amplifiertype 2635 (serial 

### no. 1006781)and recordingswere made using a Sony 

### DAT recorder type TCD-D7 (serial no. 73734). 

### The recordings made were calibrated using a 400mV, lOOOHz signal from signal generator and a Goldstar 20MHz 

### type OS-9020A 

### oscilloscope (serial no. 

### 4010355). As 

### with the environmental survey, the DAT 

### recordings were examined audibly and were analysed using computer software.
Measurements were made at a series of 

### fifteen positions in the region of 

### the water inlet channel with the improved deterrent system klly 

### operational. These consisted 

### of 

### three lines 

### of measurement points. Figure 22 

### is a map 

### of the area indicating the positions at which measurements were taken. Line 1 comprised 

### of measurement points along a line parallel to the axis 

### ofthe inlet channel 

### 15mto the west ofthe centreline. Line 2 comprised of measurement points along the centreline of the inlet channel. Line 3 

### comprised of measurement points along a line parallel to the axis ofthe inlet channel 15mto the west 

### of the centreline. Along each 

### line, five measurements were made at distances 

### of 12, 20, 30, 

### 40 and 

### 50m fiom

### the intake. Thesepositions are referred to in 

### this report as measurement points 1-1 to 1-5, 2-1 to 2-5 

### and 3-1 to 3-5. 

### For example position 1-4 

### represents a measurement point 40m along the inlet channel 

### from the water intake, 15mwest 

### from the inlet channel centreline.Positional information was acquired 

### by means 

### of 

### an optical range finder.

3.2 

### Results 

### Figure 13 is 

### a table 

### of the broadband sound pressure levels measured 

### in the water inlet channel,in the positions indicated in 

### figure 12. 

### Figure 14 

### is a graph ofthe broadband sound pressure levels at the points of measurement in the water inlet channel. It is evident that the levels recorded 

### along line 3 

### with the system switched on are lower than those for lines 1 

### and 2. 

### Since the background levels follow 

### a similar pattern, this 

### is evidently a characteristic 

### ofthe propagation of sound from the power stationintake along the water inlet channel.
The highest recorded sound levels along lines 1 

### and 

### 2 with the system switched on occur at positions 1-4 

### and 2-4 

### which were both 40m from the intake. This is logical since both these measurement points coincide with the positions 

### of projectors. However since the 

## 9
Document CNA184ROI02

### measurements were taken at 

### a depth 

### of 

### 5m, the projectors were below the point 

### of measurernent. The highest recorded sound level for line 3 

### with the system switched 

### on occurs at position 3-1 

### which represents a distance 

### from the intake of 

### 12m. There 

### is a second, much smallerpeak, however, the samelevel occurring at both positions 3-3 and 3­ 

### 4, distances 

### 30m and 

### 40mrespectively measurementpoints. 

### This 

### is in agreement with the previous observation of less effective propagation 

### on this side of the water inlet channel. However, the greatest signal to noise ratios occur at positions 1-4, 

### 2-4 and 3-4. The maximum effectiveness of the system would therefore appear to be 40m away fiom the intake on all three lines of measurement, 

### a distance which coincides with the position 

### of the mid-channel group 

### ofprojectors
The range of 

### the sound pressure levels measured 

### in the inlet channel 

### is relatively small. The difference between the lowest and highest values 

### of the 

### background measurements 

### is 8.4 

### dE3 and difference between the lowest and highest values with the system 

### on is 9.5 dE3. 

### This indicates that the sound field within the inlet channel is 

### fairly uniform when compared 

### to the typical sound field decay which would be experienced

### in open water. Position 2-5 

### ofthe 

### local sound field 

### survey coincides with position 2 

### ofthe environmental survey. The broadband sound pressure levels of the 

### two surveys agree well in this position despite the fact that the two surveys were conducted approximately 

### two months apart. The background noise levels are within 1dB of each other and the measurements taken with the system on present a difference of 3dB, the local sound 

### field survey indicating the higher level at this point. This can be accounted for by the fact that the additional projectors were 

### in place at the time 

### ofthe local sound field survey. Figures 15 

### and 16 

### are graphs of fiequency spectra 

### of time histones recorded in positions 1-1 

### to 1-5. These are 

### in agreement with the broadband sound pressure levels given 

### in figure 13. 

### Figure 15 

### shows the levels with the system 

### on in positions 1-1 and 1-2 

### to 

### be similarto the background noise spectra. It 

### is evident that the high levels 

### of noise close to the water intake were sufficient to substantially reduce the signal to noise ratios in this area. It 

### is interesting 

### to note the source level characteristics in the region 

### of 400% to 500Hr; 

### in figure 16. 

### The similar contours but different levels 

### in this frequency range suggest that position 1-4 experienced the highest degree 

### of direct contribution 

### from the mid-channel group of speakers and position 1-3 

### the least. Figures 17 

### and 18 

### are graphs of frequency spectra 

### of time histories recorded 

### in positions 2-1 

### to 2-5. 

### The most noticeable characteristic with the system on 

### is the higher levels below lOOHz

### and large peak in the range 400Hz 

### to 500Hz 

### in position 2-4. 

### This indicates a higher degree 

### ofdirect contribution

### fiomthe projectors than the other positionswhich 

### is as expected since this position corresponds to the mid-point 

### of the mid-channel speaker 

### group.



### 10

. . DocunientCNA184R0102Acoustic Surveysa fo FishDeterrent $stein at HartiepoolNuclear P awer Station



### Figures 19 

### and 20 

### are graphs of frequency spectra of time historiesrecorded in positions 3-1 

### to 3-5. 

### As the broadband sound pressure levels indicate, the levels with the source on are extremely similardespite their distance apart.
In 

### summary: 1) 

### Propagation alongthe east side 

### ofthe inlet channelwas not as efficient as that alongthe centre ofthe channel or along the west side. 2) 

### The largest signal to noise ratio and therefore the highest efficiency 

### of the system occurred 40m alongthe inlet channel fromthe water intake. 3) 

### The sound field was relatively uniform throughout the inletchannel. 4) The measurementpoint common 

### to both the 

### environmental measurements and the local 

### sound field measurementsindicated significant agreementbetween the two surveys.



### 11
SubacoustechLtd I995 Document CNAi84RO1024. 

### Discussion
The biological investigation of the fish catch showed the deterrent system to be effective during the period of the trial 

### installation at Hartlepool. The measurements of the sound field within the inlet channel indicate that the signal to noise ratio 

### of up to 

### 15.5dB was sufficient for the system to act 

### as a fish deterrent, the point 

### of maximum effectiveness coinciding with the position of the mid-channel group of projectors. The measurements made 

### in Seaton channel indicate that the signd had decayed tothat 

### of background within a maximum of225m 

### fiom the water intakein all directions. Figure 21 

### is a graph 

### of the broadband sound pressure levels along the centre 

### of the inlet channel for system both switched on and switched 

### off Both these plots have been extrapolated linearly to indicate the distance along the axis 

### of the water inlet channel at which the background noise fiom the power station and the signal level 

### fi-omthe deterrent system might be expected to decay to 

### the average background level recorded in Seaton channel which was 1 1SdB re 1pPa. The level with the system switched 

### on decays along the axis 

### of the inlet channel to the average background level within 200m. Ideally, the 

### signal to noise ratio within the inlet channel should be 

### as high as possible to maximise effectiveness but 

### with the signal decaying to background rapidly with increasing distance. 

### The system could therefore be enhanced by 

### increasing the source level and therefore the signal to noise ratio, within the inlet channel, without risk 

### of adverse effects 

### on the seal colony. As illustrated 

### in figure 21 

### it is 

### estimated that 

### the acoustic field created by an increase 

### in source level of 

### as much as 20&, 

### which represents 

### a tenfold increase 

### in sound pressure, would still decay to background level at a distance of 270m.



### 12
SubucoustechLtd 1995 Document CNA184R01025. 

### Conclusions
A number of

### conclusions can be drawn from the two acoustic surveysundertaken. Generally: 1) Both surveys measurements indicated that the sound field was extremely well confined within the water inlet channel. Both the background noise and the deterrent signal levels within the inlet channel were significantly higher than the surrounding area 

### of Seaton Channel and the sound decayed to the background level within a maximum of 225m

. It 

### is suggested that this was due to the geometry ofthe water inlet channel. 2) The propagation of 

### sound was to some degree affected by the tidal conditions, lower water levels attenuating radiation at the lower end 

### of the frequency spectrum. 

### This effect was predicted by the PrISM model. 3) 

### Background 

### noise was high and mainly 

### due to the cooling water pumps. 4) 

### The effectiveness of 

### the system could possibly be further enhanced by increasing the source level and therefore the signal to noise ratio in 

### the inlet channel. An 

### increase 

### of as much as 20dB would probably stili 

### not disturb the seals since it is estimated that the signal level would have decayed to that of background within 270m from the water intake.
In the environmental context: 5)It is 

### suggested that the sound pressure levels outside the water inlet channel are not suficient to cause concern with respect to the local seal population since the sound field of 

### the deterrent system decays to the existing level 

### of background noise Within 225m of the water intake to the east and west of the inlet channel and to 8dB re 1pPa above background level at a distance of lOOm 

### from the intake along the line 

### of the water iniet channel. This is 

### well within the limits set 

### by English Nature with respect to acceptable sound pressure levels. It 

### is estimated that the sound field decays to that 

### of background along the axis of

### tile water inlet channel within 200m.
With respect to the local sound field: 6) 

### The measurements taken of 

### the local sound field indicated that sound pressure levels varied by a relatively small amount throughout the water inlet channel. 

### This 

### is due to the confined geometry of 

### the channel. The sound field in this region is 

### relatively uniform with high signd to noise ratio although propagation along the east side 

### ofthe channel was consistently lower. In 

### other words the level 

### of sound with the system operating is well above the naturally occurring levels of sound 

### in 

### this region.

SubncoiistechLtd 199sAcousticSuwqsofafishDeterreni StJsteeni atHartlepoolNuclearPower Station



### Figure 

### 1 Map of the site and the environmental survey measurementpositions

14 Suhacoustech Ltd I995 Document CNAI84ROI02

### -- AcousiicSurveysof aFishDelewent Svstertr niIiarilepool it‘uclear Power Station



### Figure 2. 

### Environmental Survey Broadband 

### Sound PressureLevels



### Position

la


### lb
2

3

4

A
�3


### C


### D


### E
F 3ackground Level 

### with Signal/Noise 

### Descriptionof level source

### an 

### ratio position



### re lpPa re 

### (d33)re 

### IpPa 

# {a> luPa 140 148 8 

### sidewall ofthe water intake 147 152 5 

### side wall 

### ofthe water intake 1

### 44 149 5 

### outer edge ofwater inlet channel 

### (50m from wall) 134 142 8 1OOm 

### fi-omwater intake wall, dead

centre 

### ofinlet channel 120 128 8 

### 150mfrom 

### water intakewall, dead

centre 

### ofinlet 

# I channel 110 110 0
110 110 0
122 122 0
0
118 

### 118 0


### 124 126 2
0
0
0
0



### 15 500m

### east 

### ofcentre ofwater inlet channel 400m east 

### ofcentre ofwater inlet channel

300m east ofcentre 

### ofwater inlet channel

200m east 

### ofcentre ofwater inlet channel

1

### OOm east 

### ofcentre of

### water inlet channel

1

### OOmwest 

### ofcentre 

### ofwater 

### inlet channel 200m west ofcentre 

### ofwater inlet channel 300111 

### west ofcentre 

### ofwater inlet channel 400m 

### west of

### centre 

### ofwater inlet channel 

### 600m west 

### of centre ofwaterinlet channel

SubacoustechLid I995 Document CNA184R0102AcousticSurveysofaFishDeterrentSystematHartlepoolNuclearPowerStation

U
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### 16 SubacoustechLtd I995 3AcoasticSzrweys ofa Fish Deterrent System at HmtlepoolNuclearPowerStation



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SubamustechLtd I995 Document CNAi84ROI 02A~~sfic SurveysofaFishDeterrent System atHartiepooiNuclear PowerStation

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SubucoustechLtd I995 DocumentCNA184RO102Acoustic Sun7e51s ofaFishDeterrenf SystematHartiepooiNuciearPowerStation

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SubacoustechLtd 1995AcousticSurveysofaRshDeterrentSystematHartleepoolNaclearPowerStation

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## 21 SubacoustechLtd I995 Document CXA184RO102AcousticSurveys of aFishDeterrentSystem at HnrtlepoolNtlcienrPower Station

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Subaeoustech Lrd 1995 Document CNA184RO102Acoistic SurveysofaFishDeterrentSptematHmtlepooiNuclearPowerStation



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Subacoustech Ltd I995 Document CNAf84ROi02AcousticSurveysofaFishDeterrentSystem atHartlepoolNuclearPowerStation I



### 24
Subacoastech Ltd 1995 DmmentCNAf84R0102AcousticSurveysofaFishDeterrentSystem atHartlepoolNuclearPower Statim /



### 2 0 .L. Y .I 

### 3 a Y E Q) E Q) L 

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### 25
SubacoustechLtd 1995 Document CNA184ROI02

### Figure 

### 13. Environmental 

### Survey Broadband 

### Sound Pressure Levels



### Position Distance 

### of 

### position from waterintake 

### (dB) re 

### re l@a centreline 

### (m) 12

~ 1-2 20 

### 15mWest 146.3 

# 1 151.7 

# I 5.4 1-3 30 15mWest 147.3 152.3 5.0 

### 1-4 

# 1 40 

### 15m

### West 

# 1 145.7 156.8 11.1
Om Om 

# 1 146.8 146.8 

# 1 153.1 151.4 6.3 

### 4.6 

# i
Om 145.7 154.4 8.7 

### Om 

## I 142.2 157.7 

### 15.5


### 15mEast 

### 1 145.1 

### 1 150.8 

### 1 5.7 

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